Henry George Liddell, Robert Scott, A Greek-English Lexicon

A.ao and εω; Dor. ᾿Αΐδας, α, used by Trag., in lyr.and anap.: gen. ῎Αϊδος, dat. ῎Αϊδι, Hom., Trag., v. infr.: (perh. ἀ- priv., ἰδεῖν):—in Hom. only as pr.n. Hades, “Ζεὺς καὶ ἐγώ, τρίτατος δ᾽ Αΐδης” Il.15.188, cf.Hes.Th.455:—εἰν᾽ Αΐδαο δόμοισι in the nether world, Od.4.834; freq. εἰν, εἰς Αΐδαο (sc. δόμοις, δόμους), as Il.22.389, 21.48; εἰν Ἄϊδος Il 24.593; Trag. and Att. ἐν Ἅιδου, εἰς Ἅιδου (sc. οἴκῳ, οἶκον), S.Aj.865, Ar.Ra.69, etc.; Ἄϊδόσδε, Adv. to the nether world, Il.7.330, etc.; παρ᾽ Ἅιδῃ, παρ᾽ Ἅιδην, OT972, OC 1552:—hence,

2. place of departed spirits, first in Il.23.244 “εἰσόκεν αὐτὸς . . Ἄϊδι κεύθωμαι; ἐπὶ τὸν ᾄδην” Luc.Cat.14; “εἰς ἀΐδην” AP11.23; “ἐν τῷ ᾄδῃ” Ev.Luc.16.23.

II. after Hom., the grave, death, ἀΐδαν λαγχάνειν, δέξασθαι, Pi.P.5.96, I.6(5).15; ᾄδης πόντιος death by sea, A.Ag.667, cf. E.Alc.13, Hipp.1047; ᾄδου πύλη, Astrol., region below the Horoscope, Vett.Val.179.13.

2. gen. ᾄδου with nouns in adjectival sense, devilish, “θύουσαν ᾄ. μητέρ᾽” A.Ag.1235; “ᾄ. μάγειρος” E.Cyc.397; fatal, deadly, δίκτυον, ξίφη ᾄ., A.Ag.1115, E.Or.1399. [α^ Hom. in all forms exc. α_ι^δος before vowels; α_ι^δης Semon.7.117, prob. in S.OC1689.]