A double-headed horizontal arrow with harpoons pointing outward, representing logical equivalence or bidirectional implications in formal logic.
Examples
Logical equivalence between statements
P \Harr Q \text{ means P if and only if Q}
Mathematical equivalence relation
x^2 = 4 \Harr x = \pm 2
Set equivalence
A \cap B = \emptyset \Harr A \text{ and } B \text{ are disjoint}