A map is called bijective if it is both injective and surjective. A bijective map is also called a bijection.
A function 
admits an inverse 
(i.e., "
is invertible") iff
it is bijective.
Two sets 
and 
are called bijective if there is a bijective map from 
to 
.
In this sense, "bijective" is a synonym for "equipollent"
(or "equipotent"). Bijectivity is an equivalence
relation on the class of sets.
