One-one is also known as injective.
Onto is also known as surjective.
Both one-one and onto are known as bijective .
Check whether the following are bijective.
Function is one one and onto.
∴ It is bijective
Function is one one and onto.
∴ It is bijective
Function is not one one and not onto.
∴ It is not bijective
Function is one one but not onto.
∴ It is not bijective