onto

Arriving upon or on top of (speaking of a physical or metaphorical movement).

• My cat just jumped onto the keyboard.
• A new drug has just come onto the market.

Aware of.informal

• The thought-police were onto my plans of world domination.

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.

Attaining each of the values in its codomain; having its image equal to its codomain.not-comparable

• 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.