# What does this symbol mean?

1. Dec 18, 2011

### Tosh5457

This one in this context

I never understood what it means and I can't find its meaning...

2. Dec 18, 2011

### D H

Staff Emeritus
It means union. In this particular case, it is the union, for all subsets G of the set T, of the sets of ordered pairs of the elements constructible from the set G.

In other words, it is the set of all mappings (of functions) of T into itself.

Last edited: Dec 18, 2011