Wiktionary:About Proto-Brythonic

Proto-Brythonic is the last common ancestral stage of the Brythonic languages: Western Brythonic Welsh, Southwestern Brythonic Breton and Cornish, and likely Cumbric as well.

• Sonorants: *l, *ll, *r, *rr, *m, *n
• Approximants: *j, *w
• Voiceless plosives: *p, *t, *k
• Voiced plosives: *b, *d, *g
• Labialized voiced plosives: *gw
• Voiceless fricatives: *f, *θ, *x, *h, *s
• Labialized voiceless fricatives: *hw
• Voiced fricatives: *β, *ð, *ɣ, *β̃

• Back rounded: *u, *o, *ọ
• Central rounded: *ʉ
• Front rounded: *ü, *ö
• Central unrounded: *a, *ɨ
• Front unrounded: *e, *ė, *i

/oɨ/ and /uɨ/ were the regular development of long /ɛː/ and /eː/, respectively, while also resulting from vocalization of certain consonants following /o/ and /u/, whence also developed /aɨ/ and (partially) /ei/.

I-dipthongs:

• Front unrounded: *ėi, *ei
• Front rounded: *üi, *öi
• Central unrounded: *aɨ
• Central rounded: *ʉɨ
• Back rounded: *uɨ, *oɨ, *ọɨ

U-diphthongs (which we spell with w):

• Front unrounded: *iw, *ɨw,*ėw, *ew
• Front rounded: *üw, *öw
• Central unrounded: *aw
• Central rounded: *ʉw
• Back rounded: *ow, *ọw

Vowel development from Proto-Celtic to Late Brythonic:

In closed pretonic and pre-pretonic syllables, *-u- and *-ɨ- had been reduced to and , respectively.

When followed by the vowel /a/ in the final syllable, the short high vowels /i/ and /u/ are lowered to /e/ and /o/, respectively.

• Proto-Celtic *wlidā > Proto-Brythonic *gwleð

This leads to a masculine-feminine distinction in some o-stem adjectives, as the masculine form continues /i/, and the feminine form now has /e/.

• Masculine *gwɨnn vs feminine *gwenn

When short back or non-high front vowels in penultimate position are followed by front high vowels or semivowels, mainly /iː/ or /j/, they are subsequently fronted and (if possible) raised:

• /e/ becomes /i/:

Short /e/ is also the only vowel that is affected by short /i/: Proto-Celtic *gʷeltis > Proto-Brythonic *gwɨlt

• /a/ becomes raised /e̝/: Proto-Celtic *rīganī (“queen”) > Proto-Brythonic *rriɣėn
• /o/ and /u/ become /y/: Proto-Celtic *ɸlowī > Proto-Brythonic *llüw

When short non-front-high vowels in any position are followed by front high vowels or semivowel /i/, /e̝/, /y/ or /j/, they are raised and/or fronted:

• /e/ and /a/ become /e̝/:
• /u/ becomes /y/:
• /o/ becomes /ø/:

/e/ and /o/ raised to /i/ and /u/ respectively before -rn-. o also raised to u before -rg-. /e/ also raised to /i/ before intervocalic -g-. These raisings may be reversed if a-affection is present.

Initial consonant mutation is essentially the same phenomenon as lenition, as well as other forms of consonant development, only now applied across word-boundaries. *esyo tegos > *esyo degoh (lenited); *esyās tegos > *esyāh tegoh > *esyāh θegoh (spirantized).

In the table below, the symbol ◌̞ is used to indicate a more weakly articulated version of a consonant, and ◌̬ to indicate a partially voiced version of a voiceless consonant; in both cases which the lenited consonant is derived from this version.

Notes:

The sequence *wo- led to *wa- in leniting positions, but was retained in non-leniting positions. This allomorphy was resolved separately in the daughter languages, with one reflex being generalized over the other.

The plural is usually formed based on the Proto-Celtic nominative plural. However, due to apocope, plural suffixes from other classes were spreading to other nouns, making it unpredictable.

Notes:

(put information about feminines, plurals and comparatives here)