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Math Content Glossary and Key Terms

This glossary gives student-friendly math definitions for middle and high school students. Use it as a quick reference during instruction, practice, and review to help students understand key vocabulary faster.

When to use this: This glossary is especially helpful when you want students to understand vocabulary in a lesson or problem set, use correct terms during explanations, review for quizzes or assessments, or build confidence with academic language in math.

How to Use This Glossary

  1. Find the right course or grade level in the sections below.

  2. Look up the term students are seeing in problems or instructions.

  3. Read the definition out loud or have students paraphrase it in their own words.

  4. Ask students to use the term in a sentence — a math sentence or a verbal explanation both work.

Grade 6 Math

Number Sense

  • Absolute Value – Distance from zero on the number line

  • Integer – Positive and negative whole numbers and zero

  • Rational Number – A number that can be written as a fraction

  • Prime Number – A number with exactly two factors

Ratios & Rates

  • Ratio – A comparison of two quantities

  • Rate – A ratio comparing quantities with different units

  • Unit Rate – A rate with a denominator of 1

  • Percent – A ratio out of 100

Expressions & Variables

  • Variable – A letter that represents an unknown number

  • Expression – Numbers and variables combined without an equals sign

  • Equation – A math sentence with an equals sign

Geometry

  • Area – Space inside a 2D shape

  • Volume – Space inside a 3D object

  • Polygon – A closed shape with straight sides

Statistics

  • Mean – The average

  • Median – The middle value

  • Data Set – A collection of numbers

Grade 7 Math

Number Operations

  • Additive Inverse – A number that adds to zero

  • Scale Factor – A number used to enlarge or shrink a figure

Proportional Relationships

  • Proportion – An equation showing two ratios are equal

  • Constant of Proportionality – The value that relates two quantities

Expressions & Equations

  • Inequality – A math sentence using <, >, ≤, or ≥

  • Solution – A value that makes a statement true

  • Like Terms – Terms with the same variable and exponent

Geometry

  • Supplementary Angles – Two angles that add to 180°

  • Complementary Angles – Two angles that add to 90°

  • Circumference – Distance around a circle

Probability

  • Probability – How likely an event is to happen

  • Sample Space – All possible outcomes

Grade 8 Math

Exponents & Powers

  • Exponent – Tells how many times a base is multiplied

  • Scientific Notation – A way of writing very large or very small numbers

Linear Functions

  • Function – Each input has exactly one output

  • Slope – How steep a line is

  • Intercept – Where a graph crosses an axis

  • Rate of Change – Change in y divided by change in x

Geometry

  • Transformation – A change in position or size

  • Congruent – Same shape and same size

  • Similar – Same shape, different size

Data Analysis

  • Scatter Plot – A graph showing the relationship between two sets of data

  • Trend Line – A line that shows a pattern in data

Algebra I

Algebraic Expressions

  • Coefficient – The number multiplied by a variable

  • Polynomial – An expression with one or more terms

  • Factoring – Writing an expression as a product

Linear Equations

  • Slope-Intercept Form – y = mx + b

  • System of Equations – Two or more equations solved together

  • Solution Set – All solutions to an equation

Functions

  • Domain – All possible input values

  • Range – All possible output values

Geometry

Plane Geometry

  • Parallel Lines – Lines that never intersect

  • Perpendicular Lines – Lines that meet at right angles

  • Triangle – A polygon with three sides

Similarity & Proof

  • Similarity – Same shape, proportional sides

  • Congruence – Same shape and size

  • Proof – A logical explanation showing something is always true

Measurement

  • Surface Area – The area covering the outside of a 3D object

  • Volume – Space inside a 3D object

Algebra II

Polynomials & Quadratics

  • Quadratic Equation – An equation with an x² term

  • Parabola – The graph of a quadratic equation

  • Vertex – The highest or lowest point on a parabola

  • Axis of Symmetry – The line that divides a parabola evenly

Advanced Functions

  • Inverse Function – A function that reverses another function

  • Piecewise Function – A function defined by more than one rule

Statistics & Probability (High School)

  • Box Plot – Shows data spread using quartiles

  • Standard Deviation – Measures how spread out data is

  • Random Sample – A sample where each item has an equal chance of being selected

  • Correlation – The relationship between two variables

Trigonometry

  • Sine (sin) – Opposite ÷ Hypotenuse

  • Cosine (cos) – Adjacent ÷ Hypotenuse

  • Tangent (tan) – Opposite ÷ Adjacent

  • Pythagorean Theorem – a² + b² = c²

  • Unit Circle – A circle with a radius of 1

Mathematical Practices (All Grades)

  • Model – Use math to represent real-world situations

  • Justify – Explain why your answer makes sense

  • Reasoning – Thinking through a problem logically

  • Proof – A step-by-step explanation that shows something is always true

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