— Free & Public
Math Dictionary
Clear, classroom-ready definitions for every math term — browse A to Z.
GRADE 2–3
Array
A set of objects arranged in equal rows and columns, used to model multiplication.
GRADE K–2
Base Ten
Our number system, grouping quantities in tens.
GRADE 2–3
Commutative Property
Order of numbers doesn’t change the result of addition/multiplication.
GRADE K–3
Decompose
Breaking a number apart into smaller parts.
GRADE 3–5
Equivalent Fractions
Fractions that name the same amount, like 1/2 and 2/4.
GRADE 1–3
Fact Family
Related addition/subtraction or multiplication/division facts.
GRADE K–5
Number Line
A line with numbers in order, used to model counting and operations.
GRADE K–4
Place Value
The value of a digit based on its position in a number.
GRADE 3–5
Quotient
The result of dividing one number by another.
GRADE 2–4
Regrouping
Trading value between place values in addition/subtraction.
GRADE K–2
Skip Counting
Counting forward or backward by a number other than one.
GRADE 1–3
Unitizing
Treating a group of items as a single countable unit.