Seven principal categories of definite expressions are pronoun, proper name, demonstrative, relative noun, a noun with al-, annexation to a definite expression, and vocative address. Each makes a referent identifiable in a different way.
Compare “he” (context), “Zayd” (proper naming), “this” (demonstration), “the one who came” (relative clause), “the man” (al-), “Zayd’s book” (annexation), and “O Zayd” (address). The form should match how the hearer can identify the intended referent.
Definite formMode of identification
PronounSpeaker, addressee, or context
Proper nameIndividual naming
DemonstrativePhysical or mental pointing
Relative nounThe relative clause
al-Familiarity or kind
IdafaRelation to a definite referent
VocativeDirect address