regular open
English edit
Etymology edit
From regular + open; apparently a backformation from regular open set.
Adjective edit
regular open (not comparable)
- (rare, mathematics, of a set) Being the interior of its closure.
- The set (0,1)∪(1,2) is open, but is not regular open, because its closure is [0,2], so the interior of its closure is (0,2).