A nominal predicate presents a property or relation ascribed to a subject. Participial and adjectival forms can present it as a recognizable state or quality rather than foregrounding the event’s occurrence.
«زيد منطلق»
Zayd is setting off.
«زيد انطلق»
Zayd set off.
Both concern departure, but the first ascribes a state or quality while the second reports the occurrence of an act. The contrast is one of presentation and contextual force.
Nominal predication does not automatically imply permanent, unending duration; that would exceed what the construction itself asserts.