Definition of onto
1
: to a position on
- We climbed onto the roof.
- Turn left onto Fifth Avenue.
2
: in or into a state of awareness about
- put me onto your methods
- was onto something that should have been pursued further
- —Bosley Crowther
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
