uccser/cs-field-guide

# Complement

Something that completes.
In numeracy, a number plus the complement of that number adds to a nice round value.

For example: in decimal, 2 + 8 = 10, so the complement of 2 is 8, and that of 8 is 2.

Note that a *complement* is different from a *compliment*, which is an expression of praise.