زَيْدٌ نَشِيطٌ — Zayd is active: Zayd is a definite, nominative mubtadaʾ; «نَشِيطٌ» the nominative predicate.
هُوَ نَشِيطٌ — He is active: هُوَ is a detached, indeclinable pronoun in the nominative position of mubtadaʾ; «نَشِيطٌ» is the khabar.
Pronouns have a syntactic case position even when their endings do not vary.