A horizontal arrow accent placed over text or expressions to indicate reverse direction or inverse mappings in algebra and category theory.
Examples
Vector notation in geometry
\overleftarrow{AB} \text{ represents the ray from B to A}
Reverse direction in graph theory
\text{The edge } \overleftarrow{PQ} \text{ points from Q to P}
Inverse mapping in category theory
F: X \to Y \text{ with inverse } \overleftarrow{F}: Y \to X