Numbers And Operations: Math Terms Explained
Plain-language definitions of every numbers and operations term your child meets in school, each with kid-friendly explanations, worked examples, and common mistakes to watch for.
Ascending order
Ascending order is arranging numbers from the smallest value to the greatest value, like climbing up a staircase of numbers.
Bar model
A bar model is a visual math tool that uses one or more rectangles (bars) to show numbers, parts, and relationships, so students can see and solve problems with fractions, ratios, and operations more clearly.
Base ten
Base ten is a number system where each place is worth 10 times the place to its right, so digits show ones, tens, hundreds, thousands, and so on.
Comparing numbers
Comparing numbers means looking at two or more numbers to decide which is greater, which is less, or if they are equal, often using the symbols >, <, and =.
Compatible numbers
Compatible numbers are numbers that are easy to work with mentally, chosen so that adding, subtracting, multiplying, or dividing can be done quickly in your head to get a close estimate of an answer.
Compose and decompose numbers
Compose and decompose numbers means breaking a number apart into parts and putting parts together to make a whole number, often using place value like ones and tens.
Counting
Counting in math is saying or writing numbers in order to find out “how many,” to compare amounts, or to follow a number pattern, including by 1s or by larger jumps like 2s, 5s, or 10s.
Descending order
Descending order is arranging numbers from greatest to least, so the biggest number comes first and the smallest number comes last.
Difference
A difference in math is the result you get when you subtract one number from another, or how far apart two numbers or quantities are.
Digit
A digit is a single numeral symbol, such as 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9, that is used to build all whole numbers and decimals using place value.
Equal to
Equal to means that two numbers or quantities have the same value, even if they look different or are written in different ways.
Estimation
Estimation is using what you know to find a quick, reasonable answer that is close to the exact amount, length, or measurement without working it out perfectly.
Expanded form
Expanded form is a way of writing a number as a sum that shows the value of each digit, using its place value.
Factor
A factor is a number or expression that is multiplied by another to make a product, so a whole number factor divides that product with no remainder.
Greater than
Greater than describes a comparison where one number, amount, or size is larger than another.
Inverse operations
Inverse operations are pairs of math operations that undo each other, such as addition and subtraction or multiplication and division, so using one after the other brings you back to your starting number.
Less than
less than describes a number or amount that is smaller in value than another number, and is written using the symbol < when comparing two values (for example, 3 < 5).
Multiple
A multiple is a number you get by multiplying a whole number by another whole number, so it can be divided evenly by that number with no remainder.
Number line
A number line is a straight line with numbers placed in order along it, with arrows showing that the numbers keep going.
Number patterns
Number patterns are sequences of numbers that follow a clear rule, such as adding the same amount each time, multiplying by the same number, or repeating in a regular cycle.
Ordinal numbers
Ordinal numbers show the position or order of things in a list, line, or sequence, such as 1st, 2nd, 3rd, 4th, and so on.
Place value
Place value is the idea that a digit’s value depends on where it is in a number, such as ones, tens, hundreds, or tenths and hundredths for decimals.
Quotient
A quotient is the result of a division problem, showing how many times one number (the divisor) fits into another number (the dividend), or how one quantity is shared or compared.
Rounding
Rounding is a way of changing a number to a nearby number that is easier to work with, usually by looking at place value and deciding whether to keep a digit the same or increase it by 1.
Skip counting
Skip counting is counting forward or backward by the same number each time, such as 2, 4, 6, 8 or 10, 20, 30, 40, instead of counting by 1s.
Standard form
Standard form is a way of writing a number or equation in a clear, agreed-on format so its important parts, like place value or key coefficients, are easy to see and use.
Sum
A sum is the result you get when you add numbers or quantities together, such as 4 + 3 = 7, where 7 is the sum.
Whole number
A whole number is a number with no fractional or decimal part, such as 0, 7, 25, or 4,302, that can be used to count or measure complete units.
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