-εια

From σ-stem adjectives in -ης (-ēs) or -ής (-ḗs) +‎ -ῐᾰ (-ĭă), equivalent to *-εσια (*-esia) and *-esih₂.

-ειᾰ • (-eiă) f (genitive -είᾱς); first declension

2. Superficially appears in abstract nouns derived from σ-stem adjectives, with the true suffix being -ῐᾰ (-ĭă)

   ‎ἀληθής (alēthḗs, “true”) + ‎-εια (-eia) → ‎ἀλήθεια (alḗtheia, “truth”)

   ‎ἐνδεής (endeḗs, “lacking”) + ‎-εια (-eia) → ‎ἔνδεια (éndeia, “lack”)

   ‎πολυμαθής (polumathḗs, “fele-knowing”) + ‎-εια (-eia) → ‎πολυμάθεια (polumátheia, “polymathy”)

   ‎ἐπιμελής (epimelḗs, “caring”) + ‎-εια (-eia) → ‎ἐπιμέλεια (epiméleia, “care”)

3. Forming action nouns from verbs, skipping an intermediate adjective in -ης

   ‎μεταμέλομαι (metamélomai, “I regret”) + ‎-εια (-eia) → ‎μεταμέλεια (metaméleia, “regret, repentance”)

   ‎ὠφελέω (ōpheléō, “I help, am useful”) + ‎-εια (-eia) → ‎ὠφέλεια (ōphéleia, “help, benefit”)

From -υς (-us, adjective suffix) or -εύς (-eús, masculine agent noun suffix) +‎ -ιᾰ (-iă, feminine suffix), equivalent to *-εϝια (*-ewia). Nouns formed with this suffix always have recessive accent, while feminine adjectives have accent on the penult if the corresponding masculine form has accent on the ultima.

-ειᾰ • (-eiă) f (genitive -είᾱς); first declension

2. Added to various stems to form feminine nouns of person or thing concerned

   ‎ἱερός (hierós, “holy”) + ‎-εια (-eia) → ‎ἱέρειᾰ (hiéreiă, “priestess”)

   ‎Καῖσᾰρ (Kaîsăr, “Caesar”) + ‎-εια (-eia) → ‎Καισᾰ́ρειᾰ (Kaisắreiă, “Caesarea”)

3. Added to adjectival stems to form a feminine form

   ‎γλυκ-ύς m (gluk-ús, “sweet”) + ‎-εια (-eia) → ‎γλυκεῖα f (glukeîa, “sweet”)