Suppose there is an automatic door to a room. That door may:
- simply let people walk in and out as they choose.
- let people walk in, but not walk out (deathtrap!)
- let people walk out, but not back in (vacant!)
- never let anyone walk in or out - the door is always closed.
Now in cases 1 & 3 only, the room is escapable. And in cases 2 & 4 only, the room is inescapable.
And in cases 1 & 2 only, the room is 'enterable'. And in cases 3 & 4 only, the room is 'unenterable'. But these aren't real words - what real words can go in their stead?
Furthermore, what word covers case 4 only? It should mean 'neither enterable nor escapable.'