\nleftarrowThe \nleftarrow command in LaTeX is used to produce a leftwards arrow with a vertical line through it, often used to denote a function or mapping that is not left invertible or to indicate a specific type of logical or mathematical relation.
Indicates that there is no left inverse from B to A.
A \nleftarrow BDenotes a function f from Y to X that is not left invertible.
f: X \nleftarrow YRepresents a logical relation where P does not follow from Q.
P \nleftarrow Q