U+21CB "⇋" Leftwards Harpoon over Rightwards Harpoon Unicode Character

U+21CB "⇋" Leftwards Harpoon over Rightwards Harpoon is a mathematical symbol used primarily in chemical notation and vector analysis to represent a reversible equilibrium or a two-way exchange between two entities. In chemistry, it often denotes a reaction that occurs simultaneously in both forward and backward directions, distinct from the double-headed arrow that indicates resonance. The symbol combines an upper left-pointing harpoon and a lower right-pointing harpoon stacked vertically, conveying the concept of mutual or bidirectional interaction. It can also appear in logic or physics contexts to signify a reciprocal relationship or a bidirectional mapping between elements.