Main Entry: ¹on·to

Pronunciation: \ˈȯn-(ˌ)tü, ˈän-\

Function: preposition

Date: 1581

1 : to a position on
2 : in or into a state of awareness about <put me onto your methods>
3 —used as a function word to indicate a set each element of which is the image of at least one element of another set <a function mapping the set S onto the set T>