essential
Ὦ τύμβος, ὦ νυμφεῖον, ὦ κατασκαφής οἴκησις αἰείφρουρος, οἷ πορεύομαι πρὸς τοὺς ἐμαυτῆς -> Tomb, bridal chamber, eternal prison in the caverned rock, whither I go to find mine own.
Sophocles, Antigone, 883
necessary: P. and V. ἀναγκαῖος.
essential essentialis N N :: essential qualities (pl.)