A one-to-one mapping is a bijection. A many-to-one mapping is a "general function" and might also be a "surjective function".
Is there a similarly technical name for a many-to-many mapping, or should I just write "many-to-many" whenever describing such a thing. Same question for a "one-to-many" mapping (perhaps "inverse general function")?
EDIT: For what I mean by a "many-to-many" mapping:
Set 1: A, B, C, D Set 2: W, X, Y, Z A maps to W B maps to W and X C and D map to Y and Z (many-to-many relationship)