What is addition in simple words?

Addition is putting numbers or amounts together to find out how many there are in all. It is the idea of getting more or combining groups into one total. The plus sign (+) is the symbol that shows addition in a number sentence.

What is addition and how do you explain it to a child?

For a child, addition can be explained as "putting together" or "counting on." For example, if there are 4 toy cars and 3 more are added, you count 4, then 5, 6, 7 to see there are 7 cars in all. Using real objects and pictures helps the idea make sense.

What is addition used for in math?

Addition is used to find totals, to compare with subtraction in fact families, and to build understanding of patterns and sequences that grow by the same amount. It is also the base for more advanced topics, such as adding fractions, decimals, and integers, and for understanding multiplication as repeated addition with equal groups.

What is the difference between addition and subtraction?

Addition combines amounts to get a larger total, while subtraction finds how much is left or how much is taken away. In equations, addition uses the plus sign (+) and subtraction uses the minus sign (−). They are inverse operations, which means one undoes the other, such as 8 + 3 = 11 and 11 − 3 = 8.

What Is Addition? Definition and Examples

How to explain addition to a child

Addition means putting things together to see how many there are in all. If you have 3 apples and get 2 more apples, you count them to find 5 apples. You can think of addition as "getting more" or as counting on from a number. The plus sign (+) is the symbol that shows addition!

Worked examples of addition

Example 1 (early grades): Adding within 20

Problem: 8 + 7 = ?

One way is to use a "make ten" strategy. Start with 8, and think, "How many more to make 10?" You need 2 more, so break 7 into 2 and 5. First add 8 + 2 = 10. Then add the remaining 5: 10 + 5 = 15. So 8 + 7 = 15.

Example 2 (upper grades): Adding multidigit decimals

Problem: 23.47 + 8.6 = ?

Line up the numbers by place value in your mind or on paper so the decimal points match: 23.47 and 8.60. Add the hundredths: 0.07 + 0.00 = 0.07, so the hundredths digit is 7. Add the tenths: 0.40 + 0.60 = 1.00, which is 1 whole. Regroup that 1 whole into the ones place. Now add the ones: 3 ones + 8 ones + 1 regrouped one = 12 ones, which is 1 ten and 2 ones. Regroup the 1 ten into the tens place. Add the tens: 2 tens + 1 regrouped ten = 3 tens, which is 30. Put it all together: 23.47 + 8.6 = 32.07.

Going deeper with addition

In the earliest grades, addition is taught as putting groups together, getting more, or counting on. Children use objects, drawings, and number lines to show that when you add, the total gets larger. They also learn basic addition facts within 20 and see that addition and subtraction are related operations in the same fact family.

As your child moves into the middle grades, addition connects to place value. They learn to add within 100, within 1,000, and then within 1,000,000 by adding ones, tens, hundreds, and so on, and regrouping when there are enough smaller units to make a larger unit. They also use properties of addition, such as the commutative property (you can add numbers in any order and get the same sum) and the associative property (you can group addends in different ways), to make mental addition easier.

Later, addition shows up with fractions, decimals, integers, and rational numbers. Students learn that subtracting a number is the same as adding its additive inverse (for example, 5 − 7 is the same as 5 + (−7)). They also use repeated addition to understand multiplication with equal groups and use addition rules to describe patterns and sequences, such as adding the same amount each time in a growing pattern.

Common mistakes with addition

Miscounting when counting on. A child might solve 7 + 4 by saying "7, 8, 9, 10" and stop at 10, forgetting to count four new numbers. The correct way is to start at 7 and count four numbers on: 8, 9, 10, 11, so 7 + 4 = 11.
Ignoring place value in multidigit addition. A student might add 34 + 25 by doing 3 + 2 = 5 and 4 + 5 = 9, then write 59 but think the 3 and 2 were just digits, not tens. The correction is to see 34 as 3 tens and 4 ones and 25 as 2 tens and 5 ones, then add tens with tens (30 + 20 = 50) and ones with ones (4 + 5 = 9) to get 59.
Not regrouping correctly. A student might add 27 + 18 and say 2 + 1 = 3 tens and 7 + 8 = 15 ones, then write 315. The correction is to regroup 15 ones as 1 ten and 5 ones, then add tens: 2 tens + 1 ten + 1 regrouped ten = 4 tens, so 27 + 18 = 45.
Misplacing the decimal point. When adding 3.5 + 2.75, a child might write 3.5 + 2.75 = 3.525 by just joining digits. The correction is to line up decimal points and add by place value: 3.50 + 2.75 = 6.25.

Where addition shows up in everyday life

Addition appears in daily life whenever amounts are combined. Children add to find a total score in a game, to see how much money they have after getting more allowance, to count how many blocks or cards they have altogether, or to figure out how many minutes are left when more time is added to a timer. Any time your child is putting groups together or getting more of something, they are using addition.

Related terms to explore

To better understand addition and how it works in number sentences, it can help to review these related ideas:

What is addition?