-ος

From Proto-Indo-European *-os.

-ος • (-os) m (genitive -ου); second declension

1. Added to verbal roots to form an o-grade action noun.

The accent is on the root.

From Proto-Indo-European *-os.

-ος • (-os) n (genitive -εος or -ους); third declension

1. Added to verbal roots to form a noun of result or an abstract noun of action.
   1. Added to the zero-grade.

      ‎ἔπᾰθον (épathon, “I experienced”, aorist) + ‎-ος (-os) → ‎πᾰ́θος (páthos, “experience, emotion”)

   2. Added to the e-grade.

      ‎μείρομαι (meíromai, “to receive as one's portion”) + ‎-ος (-os) → ‎μέρος (méros, “part”)

-ος • (-os)

1. Nominative singular of masculine and feminine second-declension nouns

   ἄνθρωπος m or f (ánthrōpos, “person”)

2. Masculine nominative singular of first- and second-declension adjectives

   ἄλλος m (állos, “other”)

3. Masculine and feminine nominative singular of second-declension adjectives

   ἄδικος m or f (ádikos, “unjust”)

4. Nominative, accusative, and vocative singular of some neuter third-declension nouns

   γένος n (génos, “kind”)

5. Genitive singular of consonant-stem or uncontracted third-declension nouns

   ὀνόματος n (onómatos, “of a name”)

6. Genitive singular of consonant-stem or uncontracted third-declension masculine or neuter adjectives

   παντός m or n (pantós, “of the whole of”)