-η

• -ᾱ (-ā), -ᾱ́ (-ā́)
• -ή (-ḗ)

From earlier -ᾱ (-ā), from Proto-Hellenic *-ā, from Proto-Indo-European *-eh₂. The earlier -ᾱ is retained in certain dialects, and in Attic after ε, ι or ρ, whence -εā, -ιā and -ρā (e.g., ἀγορά agorā).

Cognate with Latin feminine -a, from Old Latin and Proto-Italic *-ā both in names and adjectives, e.g., φυγή (phugḗ, "retreat, escape") < Proto-Hellenic *pʰugā́ < Proto-Indo-European *bʰugéh₂; at the same time, *bʰugéh₂ > Proto-Italic *fugā (preserved in Old Latin) > Classical Latin fuga.

-η • (-ē) f (genitive -ης); first declension (Attic, Epic, Ionic, Koine)

1. suffix of nouns in the first declension.
2. Added to verbal stems ending in a consonant to form an action noun.
   2. Added to o-grade of the verbal stem

      ‎τρέφω (tréphō, “to nourish”) + ‎-η (-ē) → ‎τροφή (trophḗ, “nourishment”)

   4. Added to zero-grade of the verbal stem

      ‎φεύγω (pheúgō, “to flee”) + ‎-η (-ē) → ‎φυγή (phugḗ, “flight”)

      ‎τυγχάνω (τυχ-) (tunkhánō (tukh-), “to happen”) + ‎-η (-ē) → ‎τύχη (túkhē, “fortune”)

   6. Added to e-grade of the verbal stem

      ‎στέγω (stégō, “to shelter”) + ‎-η (-ē) → ‎στέγη (stégē, “roof”)

3. Added to masculine or neuter nouns to give a feminine form.

In Attic, the suffix retains the form -ᾱ (-ā) after ε (e), ι (i) or ρ (r).

The o-grade and zero-grade derivations have the accent on the suffix.

• -ᾱ (-ā) — Aeolic, Doric

• -ος (-os)
• -ς (-s)

• Smyth, Herbert Weir (1920) “Part III: Formation of Words”, in A Greek grammar for colleges, Cambridge: American Book Company, § 859.2