Is an element of
∈
Is not an element of
∉
Number of elements in the set/cardinal number
#
Empty set/no elements/null set
∅ or { }
Subset
⊂
Not a subset
⊄
Union/all elements contained in both sets
∪
Intersection/the elements common in both sets
∩
The set that contains all elements/universal set
U
Complement/everything outside of A
A’ or Ac
Set difference/elements that are in X but not in Y
X/Y or X−Y
Equal to
=
Not equal to
≠