You may be looking for an Injective function, in which (f(a)=f(b)) -> a=b, or a Bijection function, which is both injective and surjective (ie. there is a one-to-one correspondence between sets). In mathematics, an injective function (or one-to-one function or injection) is a function which maps distinct input values to distinct output values. ... A bijective function. ...

1. redirect One to One (the canadian band)