onto

About 35.75 uses per million words.

Meaning

preposition Arriving upon or on top of (speaking of a physical or metaphorical movement).
My cat just jumped onto the keyboard.
preposition Aware of.
The thought-police were onto my plans of world domination.
preposition Being an onto function with a codomain of (see below).
The exponential function maps the set of real numbers onto the set of positive real numbers.
adjective Attaining each of the values in its codomain; having its image equal to its codomain.
Considered as a function on the real numbers, the exponential function is not onto, as it never takes on values less than or equal to zero.