Rightwards arrow

Arrows as direction markers are younger than you might expect: no clear example is known before the eighteenth century. An early one is in Bernard Forest de Bélidor’s treatise on hydraulics of 1737, where arrows show the way water flows and a water wheel turns.

Mathematics gave → several jobs. David Hilbert used it for logical implication in 1922, and G. H. Hardy placed an arrow beneath “lim” in his 1908 book A Course of Pure Mathematics, the notation behind expressions such as x → 0.