From Teflpedia

Definiteness (/ˈdefənətnəs/) is whether a specific referent is identifiable in a given context; those which can be identified as said to be definite whilst those that can’t are indefinite.

This applies to noun phrases. Definiteness in English is typically expressed using the definite article, 'the'.

We can also distinguish within time, definite time from indefinite time and within frequency, definite frequency from indefinite frequency.