What are these numbers called?

Question

Say I have numbers that are all multiple of 2, I would say, well they are multiples of two. How are numbers $x$ called with respect to $a$ that are all formed like $x = a^b$?

I am assuming here that $b$ is a positive integer.

Answer 1

They are called powers of $a$ (although this is most common when $b$ is a positive integer).

Answer 2

Here are some more formal definitions:

http://en.wikipedia.org/wiki/Exponentiation

http://mathworld.wolfram.com/Power.html

Enjoy!

-A