Medieval Welsh

A Self-Instruction Course created by Heather Rose Jones

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Unit: 2c

Mutation: Lenition


The aspect of Celtic languages that the learner will probably find most unusual is mutation: changes in the initial sounds of words due to particular functions and environments. Originally, mutations were all simply a matter of the environment affecting the pronunciation. For example, if the previous word ended with a nasal sound (m, n, ng) the beginning of the next word might become nasalized. But when the language changed (especially when the old inflectional endings were lost, just before the Old Welsh period) it might happen that the conditioning environment for a sound change was lost but the sound change itself was kept.

One of the most common sound changes in this process is called "lenition" or "the soft mutation". ("Lenition" is just a fancy way of saying "softening".) Originally, this change happened to sounds that were sandwiched between vowels or certain other vowel-like sounds. As a rough description, lenition causes consonants to become more "vowel-like". Voiceless consonants such as p, t, c, become voiced (b, d, g); consonants that are already voiced (b, d) become the corresponding fricative (v, dd). A lesson later in this unit discusses how this affected sounds inside words and how they were spelled, but the term "mutation" is only used for changes in the initial sound.

The full set of sound changes that make up lenition are as follows. Letters not included in this list do not undergo lenition.

Radical (original sound) Lenited form
p b
t d
c g
b v
d dd
g *
m v
ll l
**rh **r

* Originally, [g] lenited to something resembling a voiced "ch", however by the Medieval Welsh period it simply disappears when it lenites.

** In Modern Welsh, "rh" lenites to "r". Because no distinction is made between the two in Medieval Welsh spelling, and because this course is based on written materials, we will not deal with this particular mutation. But those who have studied, or plan to study, Modern Welsh should be aware that it behaves similarly to "ll" when it lenites.


Lenition is the most common of the mutations and there are many environments and functions that cause it. You will learn them one at a time as we encounter them. To begin with, a feminine noun lenites when it comes directly after the definite article. So, to take examples from Lesson A, we get the following:

merch f girl y verch the girl
caseg f mare y gaseg the mare
gast f bitch yr ast the bitch
Here's a slightly tricky one.
gwreig f woman y wreig the woman
The "w" is acting as a consonant in this word, so the definite article appears as "y" not "yr".

Pronunciation Hint

If a word begins with "gwl-", "gwn-", or "gwr " followed by a vowel, you should normally treat them as consonant clusters, not as separate syllables. Thus "gwreig" (woman), "gwlad" (country), and "gwnaf" (I make) are all treated as one-syllable words.


As with the masculine nouns in the previous section, take each of the following feminine nouns and construct the phrases "the X", "and the X", "with the X", making sure that you have the correct form of the definite article and that you lenite the noun properly where appropriate.

noun the X and the X with the X
woman gwreig y wreig a'r wreig gan y wreig


noun category gloss
ael nf eyebrow
barv nf beard
cath nf cat
daear nf earth, land
esgeir nf leg
ffordd nf road
gorsedd nf mound, hill
gwlad nf land, country
llygoden nf mouse
morwyn nf maiden
pont nf bridge
rodd nf gift
seren nf star
taryan nf shield

Key to the Exercise

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