A double arrow symbol showing simultaneous right and left directions, commonly used for bidirectional mappings or reversible processes.
Examples
Reversible chemical reaction
H_2 + I_2 \rightleftarrows 2HI
Equilibrium relationship between sets
A \rightleftarrows B \rightleftarrows C
Bidirectional mapping between spaces
X \rightleftarrows Y \text{ via } f,g