In
mathematics, an
injective function or
injection or
one-to-one function is a
function that preserves
distinctness: it never maps distinct elements of its
domain to the same element of its
codomain. In other words, every element of the function's codomain is the
image of
at most one element of its domain. The term
one-to-one function must not be confused with
one-to-one correspondence (aka
bijective function), which uniquely maps all elements in both domain and codomain to each other, (see figures).