مَمْكِن، مَعْدُوم، مُسْتَحِيل
Possible, nonexistent, and impossible.
The possible can exist without involving an inherent contradiction, even if it does not actually exist. The nonexistent is absent in the relevant respect. The impossible involves a contradiction that blocks its realization.
A particular house planned for next year may be possible yet not constructed today. In contrast, the same thing being entirely existent and entirely nonexistent at the same instant and in the same respect is contradictory. Both kinds of subject can be discussed truly. That does not turn absence or impossibility into independent external objects.