زَيْدٌ ذَهَبَ — Zayd went away.
زَيْدٌ is the nominative subject of a nominal sentence (mubtadaʾ). ذَهَبَ is a past-tense verb whose concealed subject is «هُوَ», referring back to Zayd. The complete verbal clause, including its subject, functions as the predicate of the mubtadaʾ.