Addition
Addition is ...
... bringing two or more numbers (or things) together to make a new total.
Here 1 ball is added to 1 ball to make 2 balls: 

Using Numbers it is:  1 + 1 = 2  
And in words it is:  "One plus one equals two" 
Example: If you add 2 and 3 you get 5. You would write it like this:
2 + 3 = 5
Try It
Write this down, with the answer, using numbers:
You should get: 4 + 3 = 7
Have a Play
Drag the numbers to the two blue boxes see how addition works:
Swapping Places
Swapping the position of the numbers you are adding still gets the same result!
3 + 2 = 5  
... also ...  
2 + 3 = 5 
More Examples:
5 + 1 = 1 + 5 = 6
7 + 11 = 11 + 7 = 18
4 + 100 = 100 + 4 = 104
Practice
You get better at addition with practice, so we have:
Math Trainer  Addition (train your memory)
Kindergarten Worksheets (easy addition)
Addition Worksheets (normal and advanced)
Tips and Tricks
Learn more on our Addition Tips and Tricks page
Addition Table
You can also "look up" answers for simple addition using the Addition Table (but it is really best to learn to remember the answers).  
Example: Find 3 + 5


Larger Numbers: Addition in Columns
To add larger numbers, you can use Column Addition : 
Names
Other names for Addition are Sum, Plus, Increase, Total
And the numbers to be added together are called the "Addends": 