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Cowgill's law

Cowgill's law, named after Indo-Europeanist Warren Cowgill, refers to two unrelated sound changes, one occurring in Proto-Greek and the other in Proto-Germanic.

Cowgill's law in Greek

In Proto-Greek, Cowgill's law[1] says that a former /o/ vowel becomes /u/ between a resonant (/r/, /l/, /m/, /n/) and a labial consonant (including labiovelars), in either order.


  • núks "night" < PIE *nokʷts (cf. Lat. nox, Ved. nák < *nakts, Goth. nahts, Hitt. gen. sg. nekuz /nekʷts/)
  • phúllon "leaf" < PIE *bʰolyom (cf. Lat. folium)
  • múlē "mill" < PIE *mol-eh₂- (cf. Lat. molīna)
  • ónuks "nail" (stem ónukh-) < early PG *onokʷʰ- < PIE h₃nogʷʰ- (cf. OE nægl < PGerm *nag-laz)

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 núks and ónuks/ónukh-, where the usual Greek change *kʷ > p has not occurred).

Cowgill's law in Germanic

Cowgill's law in Germanic[2] has no relation to Cowgill's law in Greek other than having been named after the same person. It says that a PIE laryngeal /h₃/, and possibly /h₂/, turns into /k/ in Proto-Germanic when directly preceded by a sonorant and followed by /w/. This law is still controversial, although increasingly accepted. Donald Ringe (2006) accepts it;[2] Andrew Sihler (1995) is noncommittal.[1]

Examples are fairly few:

  • *kwikwaz "alive" (whence English quick) < PIE *gʷih₃-wos (cf. Lat. vīvus)
  • *unkw- "us two" (cf. Goth. unkis) < PIE *n̥h₃we (cf. Gk. nṓ; Ved. āvā́m acc. du. "us two" < *āva-ám)
  • Possibly OE tācor "husband's brother" < PIE *dayh₂wḗr (cf. Gk. dāḗr, Ved. devṛ́, Lat. lēvir)

If it becomes generally accepted, the relative chronology of this law could have consequences for a possible reconstructed phonetic value of h₃. Since Germanic /k/ results from earlier PIE /g/, and since the change occurred before Grimm's law applied (according to Ringe), the resulting change would be actually h₃w > gʷ. This would have been more likely if h₃ was a voiced velar obstruent to begin with. If h₃ was a voiced labiovelar fricative as is occasionally suggested, the change would therefore have been: ɣʷw > ɡʷ.


  1. ^ a b Sihler, Andrew L. (1995). New Comparative Grammar of Greek and Latin. Oxford University Press. ISBN 0-19-508345-8. 
  2. ^ a b Ringe, Don (2006). From Proto-Indo-European to Proto-Germanic. Oxford University Press. ISBN 978-0-19-955229-0.