Formal Languages and Automata Theory

List of Important Symbols

Symbol	Meaning	Section in which the symbol and its explanation appear first
a ∈ A	a belongs to the set A	1.1
a ∉ A	a does not belong to the set A	1.1
Ø	Empty set (Phi)	1.1.2
⇔	If and only if	1.1.3
|A|	Cardinality of A	1.1.3
A ⊆ B	A is a subset of the set B	1.1.4
A ⊂ B	A is proper subset of the set B	1.1.4
℘(A)	Power set of A	1.1.5
A ∪ B	Union of sets A and B	1.1.6
A ∩ B	Intersection of sets A and B	1.1.6
A − B	Complement of B in A	1.1.6
A′	Complement of A	1.1.6
<a, b>	Ordered pair	1.1.10
A × B	Cartesian product	1.1.11
aRb or Rab	a is related to b under the relation R	1.2
R′	Complement of relation	1.2.3
R−1	Inverse of relation R	1.2.3
F(x)	Image of x under f	1.3
F: A → B	Function ...