What does this notation mean? (Satisfiability / set notation)

Question

I am studying a satisfiablity course as a part of my computer science degree. My lecturer introduced some notation without explaining it and I can't seem to find out through Google.

Let F be a clause set i.e. a set of clauses "ANDEDed" together, where a clause is a set of variables "ORed" together.

Here's my problem:

F' = F \ {D}

What does the "F \ {D}" mean?

Any hints would be greatly appreciated!

Answer 1

In standard set parlance, it means all elements of $F$, except (possibly) for $D$. He may mean all elements of $F$ anded, excluding $D$ if $D\in F$.