δέον neut. part. of the impers. δεῖ, made into a Noun
that which is binding, needful, right, proper, Soph., Xen.; τὰ δέοντα things needful or proper, advantages or duties, Thuc., etc.; ἐν δέοντι (sc. καιρῶι), in good time, Lat. opportune, Eur.; ἐν τῶι δέοντι Hdt.; εἰς τὸ δέον for a needful purpose, id=Hdt.; hence (at Athens) the phrase for secret service, εἰς τὸ δέον ἀπώλεσα Ar.
