[Math] What does “∈” mean

Question

I have started seeing the "∈" symbol in math. What exactly does it mean?

I have tried googling it but google takes the symbol out of the search.

Answer 1

$\in$ means '(is) an element of'

For instance, 'Let $a\in A$' means 'Let $a$ be an element of $A$'

http://en.wikipedia.org/wiki/Element_(mathematics) might help you too