With external reference (العهد الخارجي), the intended individual or group is identifiable as an external referent, rather than merely a mentally available instance of a category. The link may be explicit verbal mention or a contextual cue that reliably singles out the referent.
Explicit reference: returning to a person named or mentioned earlier.
Implicit reference: recovering a referent indicated by an earlier expression without naming it directly.
Shared-knowledge or situational reference: identifying a known referent through the context even without a previous direct mention.
“Already known” does not mean the identical noun must have appeared before. The hearer's existing knowledge and the discourse can establish the reference.