Definition 5.19 (Set Operations)

Let A and B be sets

1. $\text{Intersection:}$ $A\cap B:=\{x|x\in Aandx\in B\}$
2. $\text{Union:}$ $A\cup B:=\{x|x\in Aorx\in B\}$
3. $\text{Difference:}$ $A-B:=\{x|x\in Aandx\notin B\}$
4. $\text{Symmetric Difference:}$ $A\oplus B:=(A-B)\cup (B-A)$

Note that $A-B$ is sometimes denoted by $A\mathrm{\setminus }B$,
and $A\oplus B$ by $A\mathrm{△}B$