Cowgill's law (Greek)

Cowgill's law says that a former /o/ vowel becomes /u/ between a resonant (/r/, /l/, /m/, /n/) and a labial consonant (including labiovelars), in either order. It is named after Indo-Europeanist Warren Cowgill.

Examples:

Note that when a labiovelar adjoins an /o/ affected by Cowgill's law, the new /u/ will cause the labiovelar to lose its labial component (as in Greek: núks and Greek: ónuks/ónukh-, where the usual Greek change *kʷ > *p has not occurred).