The famous disciple of Ibn Sina, in a passage taken from II.1.281.10-20 of his Kitab al-Tahsil, characterizes wujud as follows:
‘Existence which has no cause’ is prior by nature to ‘existence which has a cause’. Likewise, the existence of ‘substance’ is prior to the existence of ‘accident’. Also, some existence is stronger, and some weaker. It is clear that one cannot say: existence which is common [al-wujud al-‘amm] is predicated of ‘human being’ or of ‘donkey’, or of ‘the heavens’ in the same way [bi’l-tasawi], like ‘yellow’ or ‘red’. You will know that some bodies have priority over others. This means that the existence of these bodies has priority over the existence of others, not that one corporeality has priority over the other corporeality. Likewise, if we say that the cause has priority over the effect, this means that its existence has priority over [the effect’s] existence. Likewise, if we say: ‘two’ has priority over ‘four’, and so on. If existence is not considered, there is no priority or coming-after [i.e., posteriority]. So, priority and coming-after are what are made to subsist by existences i.e., by existents.