The following abbreviations are used on this site.
| B. | Breton |
| Br. | British |
| c. | circa, around |
| C | century (after numbers) |
| C | consonant |
| C. | Cornish |
| cf. | compare with |
| Cu. | Cumbric |
| e | early |
| E. | English |
| F. | French |
| g | genitive |
| G. | Scottish Gaelic |
| Gaul. | Gaulish |
| Gk. | Greek |
| I. | Irish |
| l | late |
| L. | Latin |
| M | Middle, Medieval |
| M. | Manx |
| Mod | modern |
| O | Old |
| ON. | Old Norse |
| PC. | Proto-Celtic |
| PGmc. | Proto-Germanic |
| PIE. | Proto-Indo-European |
| pl. | plural |
| R. | River |
| sg. | singular |
| V | vowel |
| VL. | Vulgar Latin |
| W. | Welsh |
| ‹ › | orthographic form (spelling) |
| / / | phonemic form (basic sounds) |
| [ ] | phonetic form (detailed sounds) |
| * | hypothetical/reconstructed form |
| ** | expected but unattested form |
| † | archaic or obsolete |
| > | leads to |
| < | derives from |
| : | cognates |