In mathematics, an injective function is a function which associates distinct arguments with distinct values.
An injective function is called an injection, and is also said to be an information-preserving or one-to-one function (the latter is not to be confused with one-to-one correspondence, i.e. a bijective function).
A function f that is not injective is sometimes called many-to-one. (However, this terminology is also sometimes used to mean "single-valued", i.e. each argument is mapped to at most one value.)
Reference:
http://en.wikipedia.org/wiki/Injective_function
