functional property

If a property is functional, for a given individual, there can be at most one individual that is related to the individual via the property. Take, for example, a functional property hasBirthMother. Something can only have one birth mother. If we say that the individual Jean hasBirthMother Peggy and we also say that the individual Jean hasBirthMother Margaret, then because hasBirthMother is a functional property, we can infer that Peggy and Margaret must be the same individual. It should be noted however, that if Peggy and Margaret were explicitly stated to be two dierent individuals then the above statements would lead to an inconsistency.

Functional properties are also known as singles valued properties and also features.

Note also that if a property is functional then it cannot also be transitive.