Your FREE Praxis 5511 Flashcards 2026 – 200+ Cards

Praxis 5511 Flashcards

Theme

The central message, lesson, or insight about life that a literary work conveys. It is usually implied rather than stated — for example, a story about a closed factory may carry the theme of communities lost to economic change.

Main idea

The most important point a passage makes — what the text is mostly about. Supporting details, examples, and reasons all back up the main idea, which may be stated in a topic sentence or implied.

Supporting detail

A fact, example, reason, or explanation that develops or proves the main idea. Strong readers separate central points from the details that elaborate them.

Inference

A logical conclusion the reader draws by combining clues in the text with prior knowledge. The conclusion is not stated outright but is supported by evidence in the passage.

Fact versus opinion

A fact can be verified or proven true (the river is 300 miles long); an opinion expresses a belief, judgment, or feeling that cannot be proven (the river is beautiful). Distinguishing them is key to evaluating arguments.

Author's purpose

The reason an author writes a text: to inform, to persuade, to entertain, or to explain. Recognizing purpose helps readers judge tone, word choice, and reliability.

Point of view

The perspective from which a story is told. First person uses 'I' and is limited to one narrator; third-person limited follows one character; third-person omniscient knows all characters' thoughts.

Tone

The author's attitude toward the subject or audience, conveyed through word choice — for example, sarcastic, hopeful, somber, or playful. Tone reflects the writer; mood is what the reader feels.

Mood

The emotional atmosphere a text creates in the reader, shaped by setting, imagery, and word choice — such as tense, peaceful, eerie, or joyful.

Setting

The time and place in which a story occurs, including the social and historical context. Setting can shape characters, drive conflict, and influence mood.

Characterization

How an author reveals a character's personality — directly (telling the reader) or indirectly (through the character's actions, speech, thoughts, and how others react).

Imagery

Vivid, descriptive language that appeals to the five senses — sight, sound, smell, taste, and touch — helping readers picture and feel a scene.

Metaphor

A figure of speech that states one thing IS another to draw a comparison, without using 'like' or 'as' — for example, 'time is a thief.'

Simile

A comparison of two unlike things using 'like' or 'as' — for example, 'as brave as a lion' or 'fought like a tiger.'

Personification

Giving human qualities, actions, or emotions to animals, objects, or ideas — for example, 'the wind whispered through the trees.'

Hyperbole

Deliberate, obvious exaggeration used for emphasis or effect, not meant to be taken literally — for example, 'I've told you a million times.'

Symbolism

Using an object, person, or action to represent a larger idea — for example, a dove symbolizing peace or a road symbolizing life's journey.

Foreshadowing

Hints or clues an author plants early in a text that suggest what will happen later, building suspense and anticipation.

Irony

A contrast between expectation and reality. Verbal irony says the opposite of what is meant; situational irony is when the outcome differs from what is expected; dramatic irony is when the reader knows what a character does not.

Alliteration

The repetition of the same beginning consonant sound in nearby words — for example, 'the slithering snake slid silently.'

Genre

A category of literature defined by form and content — such as fiction, nonfiction, poetry, drama, biography, or folktale. Each genre has typical features readers expect.

Fiction versus nonfiction

Fiction is invented narrative (novels, short stories, fables); nonfiction presents factual information about real people, events, or ideas (biographies, essays, articles).

Poetry

A genre that uses condensed, rhythmic, often figurative language arranged in lines and stanzas. It frequently relies on imagery, sound devices, and meter to create meaning and feeling.

Drama

A genre written to be performed, told largely through dialogue and stage directions, and divided into acts and scenes.

Fable

A short story, often with animal characters, that teaches a clear moral or lesson — such as Aesop's tale of the tortoise and the hare.

Context clues

Words and phrases surrounding an unfamiliar word that help a reader infer its meaning — through definition, example, synonym, antonym, or general sense.

Prefix

A word part added to the beginning of a base word that changes its meaning — for example, 're-' (again) in 'rewrite' or 'un-' (not) in 'unhappy.'

Suffix

A word part added to the end of a base word that changes its meaning or part of speech — for example, '-less' (without) in 'fearless' or '-tion' (act of) in 'creation.'

Root word

The base part of a word that carries its core meaning, to which prefixes and suffixes attach — for example, the Latin root 'port' (carry) in 'transport' and 'portable.'

Synonym and antonym

A synonym is a word with nearly the same meaning as another (happy/glad); an antonym is a word with the opposite meaning (happy/sad).

Denotation and connotation

Denotation is a word's literal dictionary meaning; connotation is the emotional or cultural association it carries — 'thrifty' and 'cheap' have similar denotations but different connotations.

Subject and predicate

Every complete sentence has a subject (who or what the sentence is about) and a predicate (what the subject does or is). 'The dog barked' has subject 'dog' and predicate 'barked.'

Subject-verb agreement

A verb must agree in number with its subject: singular subjects take singular verbs and plural subjects take plural verbs — 'The student writes' but 'The students write.'

Noun

A word that names a person, place, thing, or idea. Common nouns are general (city); proper nouns name specific things and are capitalized (Chicago).

Pronoun and antecedent

A pronoun (he, she, it, they) stands in for a noun; its antecedent is the noun it replaces. The pronoun must agree with its antecedent in number and gender.

Verb tense

The form of a verb that shows when an action happens — past (walked), present (walks), or future (will walk). Consistent tense keeps writing clear.

Adjective and adverb

An adjective describes a noun or pronoun (a red car); an adverb describes a verb, adjective, or other adverb and often ends in -ly (ran quickly).

Complete sentence

A group of words with a subject and a predicate that expresses a complete thought. It must stand on its own — unlike a fragment, which is incomplete.

Sentence fragment

An incomplete sentence that is missing a subject, a verb, or a complete thought — for example, 'Because the rain fell.' It should be revised into a full sentence.

Run-on sentence

Two or more independent clauses joined incorrectly without proper punctuation or a conjunction. A comma splice is one type, fixed with a period, semicolon, or conjunction.

Comma usage

Commas separate items in a series, set off introductory elements, divide independent clauses joined by a conjunction, and enclose nonessential information.

Apostrophe

A punctuation mark used to show possession (the dog's bone) or to form contractions (do not becomes don't). It is not used to make ordinary nouns plural.

Capitalization rules

Capitalize the first word of a sentence, proper nouns (names, places, days, months), the pronoun 'I', and the main words in titles.

The writing process

The recursive stages of producing writing: prewriting (brainstorming and planning), drafting, revising (improving content and organization), editing (fixing grammar and mechanics), and publishing.

Revising versus editing

Revising improves the substance of writing — ideas, organization, clarity, and word choice. Editing corrects surface errors in grammar, spelling, punctuation, and mechanics.

Thesis statement

A single sentence that states the main claim or central argument of an essay, usually near the end of the introduction, guiding the whole piece.

Topic sentence

The sentence, usually at the start of a paragraph, that states the paragraph's main idea. The rest of the paragraph supports it with details.

Audience and purpose

Effective writers adjust their word choice, tone, and level of formality to fit their intended audience and their reason for writing — informing, persuading, or entertaining.

Text structure

The organizational pattern of a passage — chronological/sequence, cause and effect, compare and contrast, problem and solution, or description. Recognizing structure aids comprehension.

Summary versus paraphrase

A summary restates only the main points of a text in condensed form; a paraphrase restates a passage fully in one's own words at roughly the same length. Both avoid the original wording.

Place value

The value a digit has because of its position in a number. In $4{,}873$ the digit $8$ means $8 \times 100 = 800$.

Order of operations

The agreed sequence for evaluating expressions — PEMDAS: Parentheses, Exponents, Multiplication and Division (left to right), then Addition and Subtraction. So $2 + 3 \times 4 = 2 + 12 = 14$.

Prime and composite numbers

A prime number has exactly two factors, $1$ and itself (such as $2, 3, 5, 7$); a composite number has more than two factors (such as $4, 6, 9$). The number $1$ is neither.

Greatest common factor (GCF)

The largest whole number that divides two or more numbers evenly. The GCF of $12$ and $18$ is $6$. It is used to simplify fractions.

Least common multiple (LCM)

The smallest positive number that is a multiple of two or more numbers. The LCM of $4$ and $6$ is $12$. It is used to find common denominators.

Equivalent fractions

Different fractions that represent the same value, formed by multiplying or dividing the numerator and denominator by the same nonzero number: $\dfrac{1}{2} = \dfrac{2}{4} = \dfrac{3}{6}$.

Adding and subtracting fractions

Rewrite the fractions with a common denominator, then add or subtract the numerators: $\dfrac{1}{3} + \dfrac{1}{6} = \dfrac{2}{6} + \dfrac{1}{6} = \dfrac{3}{6} = \dfrac{1}{2}$.

Multiplying fractions

Multiply the numerators together and the denominators together, then simplify: $\dfrac{2}{3} \times \dfrac{3}{4} = \dfrac{6}{12} = \dfrac{1}{2}$.

Dividing fractions

Multiply the first fraction by the reciprocal of the second: $\dfrac{1}{2} \div \dfrac{3}{4} = \dfrac{1}{2} \times \dfrac{4}{3} = \dfrac{4}{6} = \dfrac{2}{3}$.

Converting fractions and decimals

Divide the numerator by the denominator to get a decimal: $\dfrac{3}{4} = 0.75$. To convert a decimal to a fraction, write the digits over the place value: $0.6 = \dfrac{6}{10} = \dfrac{3}{5}$.

Percent

A ratio comparing a number to $100$. To find a percent of a number, multiply by the decimal form: $25\%$ of $80$ is $0.25 \times 80 = 20$.

Percent change

The amount of increase or decrease as a percent of the original: percent change $= \dfrac{\text{new} - \text{old}}{\text{old}} \times 100$. Going from $40$ to $50$ is a $25\%$ increase.

Ratio

A comparison of two quantities by division, written as $a:b$ or $\dfrac{a}{b}$. A ratio of $3$ cups flour to $2$ cups sugar is $3:2$.

Proportion

An equation stating that two ratios are equal: $\dfrac{a}{b} = \dfrac{c}{d}$. Solve by cross-multiplying: if $\dfrac{3}{4} = \dfrac{x}{12}$, then $4x = 36$ and $x = 9$.

Unit rate

A rate with a denominator of $1$, such as miles per hour or price per item. If $6$ apples cost $\$3$, the unit rate is $\$0.50$ per apple.

Estimation and rounding

Replacing numbers with nearby, easier values to approximate an answer. Rounding $487$ to the nearest hundred gives $500$; estimation checks whether a calculated answer is reasonable.

Variable

A symbol, usually a letter, that represents an unknown or changing number — for example, $x$ in the expression $3x + 5$.

Algebraic expression

A combination of numbers, variables, and operations with no equals sign — such as $4x - 7$. It can be evaluated when the variable's value is known.

Evaluating an expression

Substituting given values for the variables and simplifying. For $2x + 3$ when $x = 4$: $2(4) + 3 = 11$.

Combining like terms

Adding or subtracting terms that have the same variable raised to the same power: $3x + 5x = 8x$, and $7y - 2y = 5y$. Constants combine separately.

Solving a linear equation

Isolate the variable using inverse operations on both sides. For $2x + 5 = 13$: subtract $5$ to get $2x = 8$, then divide by $2$ to get $x = 4$.

Distributive property

Multiplying a factor across a sum: $a(b + c) = ab + ac$. For example, $3(x + 4) = 3x + 12$.

Inequality

A statement that two quantities are not equal, using $<, >, \le,$ or $\ge$. When multiplying or dividing both sides by a negative, reverse the inequality sign.

Coordinate plane

A grid formed by a horizontal x-axis and vertical y-axis meeting at the origin $(0,0)$. Points are located by ordered pairs $(x, y)$.

Slope

The steepness of a line, equal to rise over run: $m = \dfrac{y_2 - y_1}{x_2 - x_1}$. A positive slope rises left to right; a negative slope falls.

Slope-intercept form

A linear equation written as $y = mx + b$, where $m$ is the slope and $b$ is the y-intercept (where the line crosses the y-axis).

Function

A relationship that assigns exactly one output to each input. Tested with the vertical line test: if any vertical line crosses a graph more than once, it is not a function.

Perimeter

The total distance around the outside of a two-dimensional figure, found by adding all side lengths. A rectangle's perimeter is $P = 2l + 2w$.

Area of a rectangle

The space inside a rectangle, found by multiplying length times width: $A = l \times w$. A rectangle $5$ by $3$ has area $15$ square units.

Area of a triangle

Half the base times the height: $A = \dfrac{1}{2} b h$. A triangle with base $8$ and height $5$ has area $20$.

Circumference of a circle

The distance around a circle: $C = 2\pi r$ or $C = \pi d$, where $r$ is the radius and $d$ the diameter.

Area of a circle

The space inside a circle: $A = \pi r^2$, where $r$ is the radius. A circle with radius $3$ has area $9\pi \approx 28.3$ square units.

Volume of a rectangular prism

The space inside a box: $V = l \times w \times h$ (length times width times height). A box $2$ by $3$ by $4$ holds $24$ cubic units.

Pythagorean theorem

In a right triangle, the square of the hypotenuse equals the sum of the squares of the legs: $a^2 + b^2 = c^2$. For legs $3$ and $4$, the hypotenuse is $5$.

Types of angles

An acute angle is less than $90^\circ$; a right angle equals $90^\circ$; an obtuse angle is between $90^\circ$ and $180^\circ$; a straight angle equals $180^\circ$.

Unit conversion

Converting a measurement from one unit to another using known relationships — for example, $1$ foot $= 12$ inches, so $3$ feet $= 36$ inches. In metric, prefixes scale by powers of $10$.

Scale and proportion in models

A scale relates a model or map measurement to a real distance. If a map scale is $1$ inch $= 50$ miles, then $3$ inches represents $150$ miles.

Mean (average)

The sum of all values divided by how many there are. For $4, 8, 6$: $\dfrac{4 + 8 + 6}{3} = 6$.

Median

The middle value of a data set arranged in order. For an even count, average the two middle numbers. The median resists outliers better than the mean.

Mode

The value that appears most often in a data set. A set can have one mode, more than one mode, or no mode at all.

Range

A measure of spread equal to the greatest value minus the least value in a data set. For $3, 7, 10$, the range is $10 - 3 = 7$.

Probability

The likelihood of an event, equal to favorable outcomes divided by total possible outcomes, ranging from $0$ to $1$. Rolling a $4$ on a die has probability $\dfrac{1}{6}$.

Independent and dependent events

Independent events do not affect each other's outcome (two coin flips); for dependent events one outcome changes the next (drawing cards without replacing them).

Interpreting a bar graph

A bar graph compares amounts across categories using the height or length of bars. Read the axis labels and scale to compare values and identify the greatest or least.

Interpreting a line graph

A line graph shows how a quantity changes over time, with a line connecting plotted points. Rising lines show increases; falling lines show decreases; slope shows the rate.

Interpreting a circle graph

A circle (pie) graph shows parts of a whole as sectors, with the entire circle equal to $100\%$. A $90^\circ$ sector represents one-quarter of the total.

Translating word problems

Expressing a word problem algebraically: 'five more than twice a number' becomes $2x + 5$. Key words signal operations — 'sum' means add, 'product' means multiply.

Exponent

A small raised number showing how many times a base is multiplied by itself: $2^3 = 2 \times 2 \times 2 = 8$. Any nonzero number to the power $0$ equals $1$.

Square root

A value that, when multiplied by itself, gives the original number: $\sqrt{36} = 6$ because $6 \times 6 = 36$. It is the inverse of squaring.

Reading and ordering numbers

Comparing values using place value, decimals, and number lines. To order $0.5, 0.45, 0.6$, align decimals: $0.45 < 0.5 < 0.6$.

Declaration of Independence

The 1776 document, drafted mainly by Thomas Jefferson, declaring the thirteen colonies independent from Britain and asserting that all are created equal with rights to life, liberty, and the pursuit of happiness.

U.S. Constitution

The supreme law of the United States, ratified in 1788, that establishes the framework of the federal government, divides power among three branches, and defines the relationship between the national and state governments.

Bill of Rights

The first ten amendments to the Constitution, ratified in 1791, guaranteeing individual liberties such as freedom of speech, religion, the press, the right to bear arms, and protection against unreasonable searches.

Separation of powers

The division of federal government into three branches — legislative (Congress, makes laws), executive (the President, enforces laws), and judicial (the courts, interprets laws) — to prevent any one branch from gaining too much power.

Checks and balances

The system that lets each branch of government limit the others — for example, the President can veto laws, Congress can override vetoes and impeach, and courts can rule laws unconstitutional.

Federalism

The division of power between a national (federal) government and state governments, with some powers shared and others reserved to each level.

Three branches of government

The legislative branch (Congress) makes laws; the executive branch (President) enforces laws; the judicial branch (Supreme Court and lower courts) interprets laws and resolves disputes.

Legislative branch

Congress, made up of the Senate (two senators per state) and the House of Representatives (apportioned by population). It writes and passes federal laws and controls spending.

Rights and responsibilities of citizens

U.S. citizens have rights such as voting and free speech, and responsibilities such as obeying laws, paying taxes, serving on juries, and participating in civic life.

Democracy versus other systems

In a democracy, power rests with the people, who govern directly or through elected representatives. This contrasts with monarchy (rule by a king/queen), dictatorship (rule by one person), and oligarchy (rule by a few).

Suffrage and voting

Suffrage is the right to vote. It expanded through amendments: the 15th (race), the 19th (women, 1920), and the 26th (age 18). Voting is a core form of civic participation.

American Revolution

The 1775–1783 war in which the thirteen colonies won independence from Great Britain, driven by disputes over taxation without representation and self-government.

Civil War

The 1861–1865 conflict between the Union (North) and the Confederacy (South), fought largely over slavery and states' rights, ending in Union victory and the abolition of slavery.

Abraham Lincoln

The 16th U.S. president, who led the Union through the Civil War, issued the Emancipation Proclamation freeing enslaved people in Confederate states, and delivered the Gettysburg Address.

Emancipation Proclamation

Lincoln's 1863 order declaring enslaved people in Confederate-held territory to be free, shifting the war's purpose toward ending slavery and paving the way for the 13th Amendment.

Reconstruction

The period after the Civil War (1865–1877) when the nation worked to rebuild the South and integrate freed people, marked by the 13th, 14th, and 15th Amendments.

Industrial Revolution

The shift from hand production to machine manufacturing in factories during the 18th and 19th centuries, transforming economies, cities, transportation, and daily life.

Immigration and cultural diffusion

The movement of people into a country, bringing languages, customs, foods, and ideas that spread and blend with existing cultures — a major force in U.S. social history.

Civil rights movement

The mid-20th-century struggle to end racial segregation and discrimination in the United States, led by figures such as Martin Luther King Jr., producing laws like the Civil Rights Act of 1964.

Susan B. Anthony

A leader of the 19th- and early 20th-century women's suffrage movement in the United States whose work helped lead to the 19th Amendment, which granted women the right to vote.

Mohandas Gandhi

The leader of India's independence movement against British rule who championed nonviolent civil disobedience, influencing civil rights movements worldwide.

Eleanor Roosevelt

A U.S. first lady and human rights advocate who chaired the United Nations committee that produced the Universal Declaration of Human Rights in 1948.

World War II

The global conflict of 1939–1945 between the Allied and Axis powers, ending with Allied victory, the Holocaust's exposure, and the United States and Soviet Union emerging as superpowers.

Ancient civilizations

Early societies such as Mesopotamia, Egypt, Greece, and Rome that developed writing, law, government, and technology, laying foundations for later cultures.

Renaissance

A period of renewed interest in art, learning, and classical knowledge in Europe from roughly the 14th to 17th centuries, producing advances in science, painting, and humanist thought.

Primary versus secondary source

A primary source is firsthand evidence from the time studied (a letter, photo, or the Constitution); a secondary source interprets or analyzes primary sources (a textbook or article).

Five themes of geography

Location, place, human-environment interaction, movement, and region — the framework geographers use to organize the study of the Earth and human activity.

Latitude and longitude

Lines of latitude run east-west and measure distance north or south of the equator; lines of longitude run north-south and measure distance east or west of the prime meridian. Together they locate any point on Earth.

Map elements

Tools that make a map usable: the title, legend or key (explains symbols), compass rose (directions), and scale (relates map distance to real distance).

Human-environment interaction

The ways people adapt to, depend on, and modify their natural surroundings — such as building dams, farming, or constructing cities — and the consequences of those changes.

Continents and oceans

Earth's seven continents are Africa, Antarctica, Asia, Australia, Europe, North America, and South America; its major oceans are the Pacific, Atlantic, Indian, Arctic, and Southern.

Region

An area defined by shared features — physical (a desert), cultural (a language area), or political (a state or country). Geographers use regions to organize and compare places.

Supply and demand

Demand is how much consumers want at various prices; supply is how much producers offer. Price tends to settle where the two meet — the equilibrium price.

Scarcity

The fundamental economic problem that resources are limited while human wants are unlimited, forcing individuals and societies to make choices about how to use them.

Opportunity cost

The value of the next-best alternative given up when a choice is made. Choosing to spend money on one item means forgoing what that money could have bought instead.

Goods and services

Goods are tangible products you can touch (food, cars); services are intangible actions performed for others (teaching, haircuts). Both satisfy economic wants.

Producers and consumers

Producers make goods or provide services; consumers buy and use them. The flow of money and resources between them drives a market economy.

Market economy

An economic system in which prices, production, and distribution are determined mainly by supply and demand and private decisions, with limited government control.

Money and trade

Money is a medium of exchange, a store of value, and a unit of account that makes trade easier than bartering. Trade lets people and nations specialize and exchange surpluses.

Imperialism

A policy of extending a nation's power by acquiring colonies or controlling other territories economically and politically, prominent in the 19th and early 20th centuries.

Branches' powers: judicial

The judicial branch interprets laws and the Constitution. Through judicial review, established in Marbury v. Madison (1803), courts can declare laws unconstitutional.

Amendment process

The Constitution can be changed by an amendment, typically proposed by a two-thirds vote of both houses of Congress and ratified by three-fourths of the states.

Taxation

The collection of money by governments from citizens and businesses to fund public services such as schools, roads, and defense. Paying taxes is a civic responsibility.

Westward expansion

The 19th-century movement of U.S. settlers westward, encouraged by ideas like Manifest Destiny, which displaced Native American nations and reshaped the continent.

Native American nations

The diverse Indigenous peoples who lived across the Americas before and after European contact, with distinct cultures, governments, and lands later affected by colonization and expansion.

European exploration

The 15th- and 16th-century voyages by nations such as Spain, Portugal, England, and France that connected Europe, Africa, and the Americas and launched colonization.

Cold War

The post-WWII period of political and military tension (roughly 1947–1991) between the United States and the Soviet Union, marked by an arms race, proxy wars, and ideological rivalry.

Civic participation

The ways citizens engage in their communities and government — voting, volunteering, serving on juries, contacting officials, and staying informed — sustaining a democracy.

Fact versus opinion in documents

Reading historical documents critically by separating verifiable facts from the author's beliefs or perspective, and recognizing that sources may reflect bias or limited viewpoints.

Multiple perspectives in history

Recognizing that an event can be understood differently depending on who is telling it, and that historians weigh varied sources to build a fuller, more accurate account.

Scientific method

A systematic process of inquiry: ask a question, form a hypothesis, design and conduct an experiment, collect and analyze data, and draw a conclusion based on evidence.

Hypothesis

A testable, tentative explanation or prediction for an observation, often stated as an if-then statement. It can be supported or rejected by experimental evidence but is never 'proven' absolutely.

Theory versus hypothesis

A hypothesis is a single testable prediction; a scientific theory is a well-supported, broad explanation backed by extensive evidence (such as the theory of evolution). A theory is far stronger than a guess.

Independent and dependent variables

The independent variable is the factor the experimenter changes; the dependent variable is what is measured in response. Controlled variables are kept constant to ensure a fair test.

Control group

The group in an experiment that does not receive the treatment, used as a baseline for comparison with the experimental group to judge the effect of the variable being tested.

Cell

The basic structural and functional unit of all living things. Organisms may be single-celled or multicellular, and cells carry out the processes that sustain life.

Plant versus animal cells

Both have a nucleus, cytoplasm, and cell membrane. Plant cells additionally have a rigid cell wall, chloroplasts for photosynthesis, and a large central vacuole; animal cells do not.

Photosynthesis

The process by which plants convert sunlight, water, and carbon dioxide into glucose and oxygen: \ce{6CO2 + 6H2O -> C6H12O6 + 6O2}, using energy from the sun captured by chlorophyll.

Cellular respiration

The process cells use to release energy from glucose: \ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O}, producing usable energy. It is essentially the reverse of photosynthesis.

Ecosystem

A community of living organisms interacting with one another and with their nonliving environment (water, soil, air, sunlight) in a particular area.

Food chain and food web

A food chain shows the flow of energy from producers to consumers (grass to rabbit to fox); a food web links many overlapping food chains in an ecosystem.

Producers, consumers, decomposers

Producers (plants) make their own food; consumers eat other organisms; decomposers (fungi, bacteria) break down dead matter, recycling nutrients back into the ecosystem.

Genetics and heredity

The study of how traits pass from parents to offspring through genes, which are segments of DNA. Each parent contributes alleles that determine inherited characteristics.

DNA

Deoxyribonucleic acid, the molecule that carries genetic instructions in living organisms, shaped as a double helix and made of paired bases that encode traits.

Dominant and recessive traits

A dominant allele masks a recessive one when both are present. A recessive trait appears only when an organism has two recessive alleles, as in classic Punnett-square genetics.

Natural selection

The process by which organisms better adapted to their environment tend to survive and reproduce more, passing favorable traits to offspring — the mechanism of evolution Darwin described.

Matter and its states

Matter is anything with mass and volume. Its common states are solid (fixed shape and volume), liquid (fixed volume, takes container's shape), and gas (fills its container).

Physical versus chemical change

A physical change alters form but not identity (ice melting, paper torn); a chemical change forms new substances (rust, burning, baking) and is usually hard to reverse.

Atom

The smallest unit of an element that retains its properties, made of protons and neutrons in a nucleus surrounded by electrons. Atoms combine to form molecules.

Element versus compound

An element is a pure substance of one kind of atom (oxygen, \ce{O2}); a compound is two or more elements chemically bonded in fixed ratios (water, \ce{H2O}).

Periodic table

A chart that organizes all known elements by increasing atomic number, grouping those with similar properties into columns (groups) and rows (periods).

Mixture versus solution

A mixture combines substances that keep their own properties and can be separated physically; a solution is a uniform mixture in which one substance dissolves in another (salt in water).

Acids and bases

Acids taste sour and have a pH below $7$ (such as \ce{HCl}); bases feel slippery and have a pH above $7$ (such as \ce{NaOH}). A pH of $7$ is neutral, like pure water.

Force

A push or pull that can change an object's motion or shape. Forces have both magnitude and direction and are measured in newtons.

Newton's first law

The law of inertia: an object at rest stays at rest and an object in motion stays in motion at constant velocity unless acted on by an unbalanced force.

Newton's second law

The acceleration of an object depends on the net force and its mass: $F = ma$. A larger force produces more acceleration; greater mass produces less.

Newton's third law

For every action there is an equal and opposite reaction. When you push on a wall, the wall pushes back on you with equal force in the opposite direction.

Gravity

The attractive force between objects with mass. Earth's gravity pulls objects toward its center, giving them weight and causing them to fall when dropped.

Speed, velocity, acceleration

Speed is distance over time; velocity is speed with a direction; acceleration is the rate at which velocity changes. Speeding up, slowing down, or turning are all acceleration.

Energy and its forms

Energy is the ability to do work. Forms include kinetic (motion), potential (stored), thermal, chemical, electrical, and light. Energy can change form but is not created or destroyed.

Conservation of energy

Energy cannot be created or destroyed, only transformed from one form to another. A falling ball converts potential energy into kinetic energy.

Heat transfer

Thermal energy moves by conduction (direct contact), convection (through moving fluids), and radiation (electromagnetic waves, such as the Sun's heat reaching Earth).

Electricity and circuits

An electric current is a flow of charge through a conductor. A complete circuit forms a closed loop; a series circuit has one path, while a parallel circuit has multiple paths.

Sound and light waves

Sound is a mechanical wave that needs a medium to travel; light is an electromagnetic wave that can travel through a vacuum. Both can be reflected, refracted, and absorbed.

The water cycle

The continuous movement of water through evaporation (liquid to vapor), condensation (vapor to clouds), precipitation (rain or snow), and collection in oceans, lakes, and groundwater.

Rock cycle

The ongoing process by which rocks change among three types: igneous (cooled magma), sedimentary (compacted sediments), and metamorphic (changed by heat and pressure).

Plate tectonics

The theory that Earth's outer shell is divided into moving plates whose interactions cause earthquakes, volcanoes, mountain building, and the slow drift of continents.

Earthquakes and volcanoes

Earthquakes are sudden ground movements caused by energy released along faults; volcanoes form where magma reaches the surface. Both occur mainly at tectonic plate boundaries.

Weathering and erosion

Weathering breaks rock into smaller pieces in place (by water, ice, or chemicals); erosion is the transport of those pieces by wind, water, ice, or gravity to a new location.

Weather versus climate

Weather is the day-to-day state of the atmosphere (temperature, rain, wind); climate is the long-term average of weather patterns in a region over many years.

The atmosphere

The layers of gases surrounding Earth — mostly nitrogen and oxygen — that provide air to breathe, trap heat, shield against radiation, and drive weather.

Solar system

The Sun and the objects bound to it by gravity, including the eight planets, their moons, dwarf planets, asteroids, and comets. Earth is the third planet from the Sun.

Phases of the Moon

The changing sunlit portions of the Moon we see — new, crescent, quarter, gibbous, and full — caused by the Moon's orbit around Earth over about a month.

Ocean tides

The regular rise and fall of sea level caused mainly by the gravitational pull of the Moon, and to a lesser extent the Sun, on Earth's oceans.

Stars and galaxies

Stars are massive balls of gas that produce light and heat through nuclear fusion; galaxies are vast collections of billions of stars, gas, and dust, such as our Milky Way.

Scientific tools and measurement

Instruments scientists use to observe and measure: thermometers (temperature), microscopes (small objects), balances (mass), and graduated cylinders (volume). The metric system standardizes units.

Units of measurement

Standard units quantify properties: temperature (degrees Celsius), mass (grams), length (meters), volume (liters), and energy (joules), most expressed in the metric (SI) system.

Greenhouse effect

The trapping of heat near Earth's surface by gases such as carbon dioxide (\ce{CO2}) and methane (\ce{CH4}). It keeps Earth warm, but excess gases intensify warming.

Renewable and nonrenewable resources

Renewable resources replenish naturally within a human lifetime (solar, wind, water); nonrenewable resources are finite and take ages to form (coal, oil, natural gas).

Science, technology, and society

Science and technology shape human life and the environment — affecting public health, pollution, waste disposal, and resource use — and raise choices societies must weigh.