Polymorphism

[Tina]

The capability of assuming different forms; the
capability of widely varying in form.

[Julian]

The act of [evolving] from the standard two person relationship, into something involving the loving of more than one other.
Where once a person was [monogamous], now they practice [Polyamory].

[Michiko]

the [concept] of having interchangeable [genitalia].

[Kit]

The condition of occurring in several different forms.

[Justin Bieber]

the fact that something such as an animal or organism can exist in different forms: