## What is a sum?

A sum is the result of numbers or expressions being added together. It comes from the Latin word “*summus*” which means “total”.

The first number in a sum is called the augend and the remaining numbers are called the addends.

A sum can be an unsimplified expression like the left side of this equation. Or it can be a simplified version like the right side of this equation.

A lot of elementary school teachers will say that a sum is “the answer to an addition problem” because the “answer” is a simplified version of the actual sum.

## Examples

**8 + 1 = 9**

**8**+

**1**is the sum and

**9**is the simplified sum.

**2 + 1 + 7 = 10**

**2**+

**1**+

**7**is the sum and the simplified sum is

**10**.

**7x + 5y = 12**

In this example, **7x** + **5y** is the sum.

This sum can’t be simplified because we don’t know what x and y are, but **12** is equal to the sum so you could say “**12** is the sum of **7x** and **5y**.”

**13a + 11b – 7c**

When you are working with variables, it’s usually easiest to interpret any subtraction as adding a negative.

So, in this example, you could say…

**13a + 11b**** – 7c** is the sum of the terms **13a**, **11b**, and **-7c**

Technically, you could say that **13a **is an augend, **11b** is an addend, and **-7c **is a subtrahend.

However, if any of the variables are negative numbers, that could change an addend into a subtrahend, or vice versa.

So, when we work with variables, we usually call all of the parts of the sum “terms” instead of differentiating between augends, addends, minuends, and subtrahends.

## Summation Notation

In calculus and advanced algebra, you may be asked to calculate really long (or even infinite) sums like this…

\[3+7+11+15+19+23+27+31+35…\]

These types of sums are called series and they are often written in summation notation.

## When will I use sums?

You use sums all the time because addition is one of the most basic math concepts. Almost all math problems involve addition in some way.

But sums can also be used in ways besides basic addition. The buttons below will take you to pages that explain how to use advanced sums.