Sound Changes in Brythonic Languages

The sound changes which characterise the transition from the common British language to the modern Brythonic languages of Welsh, Cornish and Breton are complex. Large volumes are filled with discussion of these developments and some of the finer details remain a mystery. However, the tables below give a general picture of the sound changes and some of the differences between the three modern languages.

Consonants

PC.	Br.	Notes	W.	C.	B.
b	b	initial intervocalic, lenited geminate	b f b	b v b	b v b
d	d	initial intervocalic, lenited geminate	d dd d	d dh d	d z d
g	g	initial intervocalic after r, l lenited geminate	g - y, a, i - g	g - gh - g	g - c'h c'h g
j	j	initial	i	y	y
k	c	initial intervocalic, lenited geminate kt	c g ch ⁱth	k g gh ⁱth	k g c'h ⁱzh
k^w	p	initial intervocalic, lenited	p b	p b	p b
l	l	initial geminate elsewhere	ll ll l	l ll, l l	l ll, l l
m	m	initial intervocalic lenited geminate, mb	m f f m	m v v m, mm	m v ñv m, mm
n	n	geminate, nd nt ng nc	n n, nn n, nh ng ngh	n n, nn ns ng nk	n nn nt ng nk
φ	-	φt > kt	- ⁱth	- ⁱth	- ⁱzh
r	r	initial intervocalic geminate	rh r r, rr	r r rr	r r rr
s	s	initial sφ st	h ff s	h f s, st	h f s, st
t	t	initial intervocalic, lenited geminate	t d th	t d, s th	t d zh
w	w	initial intervocalic	gw w	gw w	gw w

Vowels

PC.	Br.	Notes	W.	C.	B.
a	a	before -kt	a ae	a e	a e
e	e	before n/m in certain positions before -kt	e y ei, ai	e e	e ei, e
i	i	before -kt	y i	e i	e i
o	o	before n/m in certain positions before -kt	o w, y oe	o oy, o	o oa
u	u	in non-final syllables sometimes before -b, -m before -kt	w y u wy	o u oo	o, ou u oue
ā	ā	in monosyllables in final syllables in non-final syllables	aw o o	eu e o	eu e o, eu
ī	ī		i	i	i
ū	ī		i	i	i

Dipthongs

PC.	Br.	W.	C.	B.
ai	ɛ̄	oe	oo	oa
ei	ē	wy	oo	oa, oe, oue
oi	ü	u	u	u
au
eu
ou