# Definition of Additive Identity

## Overview

**Zero** is a very special number.

From the **Definition of Zero**, we know it means none or nothing.

And since zero means none or nothing,

we can **add** zero to any other number,

and the number will stay the **same**.

This **rule** in math is called the **Additive Identity**!

It doesn’t matter if the zero comes first or last in the addition problem,

the answer is still the same.

5 + 0 = 5

and

0 + 5 = 5

Here’s something else to think about.

If we add zero to itself, it will **always** be zero.

Because more of nothing is…nothing!

0 + 0 = 0

And if we subtract zero from itself, it will **always** be zero.

After all, it’s not possible to take nothing from nothing!

0 – 0 = 0

The **Additive Identity** rule in math sounds complicated, but it’s really easy!

Let’s practice!

### Practice Question 1

**Let’s add zero to a number. What’s the answer?**

5 + 0 = ____

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### Practice Question 2

**What’s the answer?**

50 + 0 = ____

### Practice Question 3

**Is this true or false?**

0 + 8 = 8

### Practice Question 4

**Is it true or false?**

10 + 0 = 0

### Practice Question 5

**What’s the missing number?**

100 + ____ = 100

____ + 100 = 100

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