LYCOS RETRIEVER 
Grimm's Law: Voiceless Stops
built 605 days ago
Grimm's Law #1: (a) A word beginning a voiceless stop such as /p/ in most Indo-European languages has for its cognate sound an aspirant /f/ in Germanic languages. (b) A word beginning in a voiceless stop such as /t/ in most Indo-European languages has as its cognate sound an aspirant /∂/ ("th") in Germanic languages. (c) A word beginning in a voiceless stop such as /k/ in most Indo-European languages has as its cognate sound an /h/ in Germanic languages.
Source:
When Grimm's law was discovered, a strange irregularity was spotted in its operation. The Proto-Indo-European (PIE) voiceless stops *p, *t and *k should have changed into Proto-Germanic (PGmc) *f, *� (dental fricative) and *x (velar fricative), according to Grimm's Law. Indeed, that was known to be the usual development. However, there appeared to be a large set of words in which the agreement of Latin, Greek, Sanskrit, Baltic, Slavic etc. guaranteed PIE *p, *t or *k, and yet the Germanic reflex was a voiced consonant (*b, *d or *g).
Source:
Grimm's law (Jakob Grimm, 1822): voiceless stops to voiceless fricatives (e.g. Latin pater, English father), voiced stops to voiceless stops (e.g. Latin dentis, English tooth), voiced aspirated stops to voiced stops (Latin hortus, English garden); exceptions to Grimm's law: preservation of voiceless stops after another voiceless stop (e.g. Latin octo, Old English eahta, Present English eight)
Source:
MORE ABOUT
Voiceless Stops