[on.to] prep (1581) 1: to a position on
2: in or into a state of awareness about "put me ~ 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 ~ the set T"
[2]onto adj (1942): mapping elements in such a way that every element in one set is the image of at least one element in another set "a function that is one-to-one and ~"