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

A.thirty years old, Pl.Lg.914b,961b (in the former place without a variant, in the latter codd. AO have τριακοντ᾽ ἔτη), PAmh.2.84.12 (ii/iii A. D.), Riv.Fil.57.379 (Aptera, iii/iv A. D.); also in forms τρια_κοντέτης (q. v.) and τρια_κοντούτης , ου, ὁ, acc. pl. “τοὺς τριακοντούτας” the men of thirty years, Pl.R.539a, Lg.670a; nom. sg. masc. “-ούτης” Gal.6.471; fem. τριακοντοῦτις , Is.6.14, CRAcad.Inscr.1932.85 (Tipasa in Mauretania).

II. of or for thirty years, “τριακονταέτεις σπονδαί” Th.5.14, X.HG5.2.2; “αἱ τριακοντούτεις σπονδαί” Th.1.23, 115, 2.2 (whence 5.14 and X. l. c. have been corrected): in fem. form, σπονδὰς τριηκοντοέτιδας (v.l. -ταέτιδας) Hdt.7.149; “σπονδαὶ τριακοντούτιδες” Ar. Ach.194, cf. Eq.1388, Th.1.87 (though elsewh. he uses the form in νς as fem., v. supr.).