onto function vs mapping

onto function and mapping both are nouns.

Word	Noun	Adjective	Verb	Adverb
onto function	Yes	No	No	No
mapping	Yes	No	No	No

As nouns, mapping is a hypernym of onto function; that is, mapping is a word with a broader meaning than onto function:

onto function: a mathematical function that is an onto mapping.
mapping: (mathematics) a mathematical relation such that each element of a given set (the domain of the function) is associated with an element of another set (the range of the function)

Other hypernyms of onto function include function, map, mathematical function, single-valued function.

onto function (noun)	mapping (noun)
a mathematical function that is an onto mapping.	(genetics) the process of locating genes on a chromosome
	the process of making maps
	(mathematics) a mathematical relation such that each element of a given set (the domain of the function) is associated with an element of another set (the range of the function)