A double-lined leftward arrow symbol commonly used to denote logical implication or mapping relations in logic and category theory.
Examples
Logical 'if' statement (converse implication)
B \Leftarrow A \text{ means 'if A then B'}
Definition or equivalence in mathematics
x \text{ is prime} \Leftarrow x \text{ has exactly two factors}
Function inverse relationship
f^{-1}(y) = x \Leftarrow f(x) = y