Leftwards Arrow with Vertical Stroke

Leftwards Arrow with Vertical Stroke at U+21F7 represents a left-pointing arrow modified by a vertical bar, often read as a barred or negated leftward arrow. It belongs to the Arrows block, a Unicode area used for directional, logical, and mathematical arrow symbols beyond the basic arrow set. In mathematics and formal logic, this character is used when an author needs to show that a leftward implication, mapping, or transition is blocked, excluded, or specially constrained. For example, in a rewrite system or state-transition diagram, A ⇷ B may be chosen to mean that movement or derivation toward the left is not allowed, depending on the notation defined by the paper or textbook. It can also appear in technical diagrams, protocol descriptions, and custom notation where a plain left arrow would be too general. Because its meaning is not standardized as tightly as common arrows like ← or ⇐, readers usually need the surrounding legend or convention to know whether the vertical stroke means “not,” “barred,” “interrupted,” or another local distinction.