Meaning of a union symbol in front of a set?

[df606]

I'm trying to read this book "Automata, Computability, and Complexity" by Elaine Rich and on page 75 it defines this function: \delta'(Q,c) = \cup\{eps(p):\exists q\in Q((q,c,p)\in\Delta)\}
I've never seen the union operator used in this way. What does it mean?
Apologies if this is in the wrong section.

Edit: I don't care what the stuff inside the brackets means. I understand that part. I'm asking, what does \cup mean when it's front of any set? It could be something like \cup\{x:x\in\mathbb{R}\}

 

[micromass]

A union in front of a set is written when the elements in the set are sets themselves. So for example, we can have

\bigcup \{A~\vert~A\in \mathcal{A}\}

this just means to take the union of each element in the set. That is:

\bigcup_{A\in \mathcal{A}}{A}

Writing \cup \{x~\vert~x\in \mathbb{R}\} doesn't make much sense since the element of \mathbb{R} aren't sets (unless you see them as Dedekind cuts).

 

[df606]

That explains things. Thanks!