Sound Laws
Sound laws describe regular phonological changes that occurred as Proto-Indo-European developed into its daughter languages. Each law captures a systematic correspondence: a PIE phoneme or cluster that reflexes predictably in one or more branches. The laws listed here are named after the scholars who first described them, and each includes the formal rule, the applicable branch, and example correspondences.
| Name | Branch | Formula | Discovered By |
|---|---|---|---|
| Bartholomae's Law | Indo-Iranian | C[+voiced, +aspirated] + C[-voiced] → C[+voiced] + C[+voiced, +aspirated] | Christian Bartholomae (1882) |
| Brugmann's Law | Indo-Iranian | PIE *o → Proto-Indo-Iranian *ā / _CV (open syllable); PIE *o → *a / _CC (closed syllable) | Karl Brugmann (1876) |
| Centum-Satem Isogloss | General | Centum: *ḱ = *k ≠ *kʷ; Satem: *ḱ → s/š ≠ *k = *kʷ | Peter von Bradke (1890) |
| Grassmann's Law | General | C[+aspirated]...C[+aspirated] → C[-aspirated]...C[+aspirated] | Hermann Grassmann (1862) |
| Grimm's Law | Germanic | PIE *p, *t, *k → PGmc *f, *þ, *h; PIE *b, *d, *g → PGmc *p, *t, *k; PIE *bʰ, *dʰ, *gʰ → PGmc *b, *d, *g | Jacob Grimm (1822) |
| RUKI Rule | General | PIE *s → *š / {r, u, K, i} _ | Multiple scholars (named as acronym of conditioning sounds) |
| The Great Vowel Shift | West Germanic | ME /iː/ → /aɪ/; ME /uː/ → /aʊ/; ME /eː/ → /iː/; ME /oː/ → /uː/; ME /ɛː/ → /iː/; ME /ɔː/ → /oʊ/; ME /aː/ → /eɪ/ | Otto Jespersen (1909) |
| Verner's Law | Germanic | PGmc *f, *þ, *h, *s → *b, *d, *g, *z when PIE accent was not on the immediately preceding syllable | Karl Verner (1875) |
| Winter's Law | Balto-Slavic | V → Vː / _ C[+voiced, -aspirated] (Balto-Slavic) | Werner Winter (1978) |