Apparently a primary word (compare "door"); a portal or entrance (the opening or the closure, literally or figuratively) -- door, gate.

θύρα (thura) − 9 Occurrences

θύραι (thurai) − 2 Occurrences

θύραις (thurais) − 2 Occurrences

θύραν (thuran) − 14 Occurrences

θύρας (thuras) − 8 Occurrences

θυρῶν (thurōn) − 4 Occurrences