FormBasic forceContextual refinement
قَامَPast occurrenceأمس can specify when
يَقُومُPresent/future scopeالآن or سـ selects a reading
قَائِمٌQuality of standingأمس or الآن can supply time
A noun is not incapable of expressing something temporal: «زَيْدٌ قَائِمٌ الآن» clearly describes a present state. The distinction is that the morphology of the verb indicates temporal orientation in a characteristic way, whereas the noun does not specify one of these times in the same fashion.