p t c b d g m ll rh
b d g f dd omit g f l r
mh nh ngh m n ng - - -
ph th ch - - - - - -
As you can see in the above table, there are nine consonants which undergo mutation in Welsh. There are three classes of mutations and different rules governing their use.
Most Welsh courses and teachers advise students not to worry too much about mutations at the outset. Fluent speakers will understand you if you forget to mutate a letter. With practice this will come naturally and there is perhaps, no need for beginning learners to make a conscious effort to apply these rules. It is important to remember, however, that mutations, "...pervade the entire structure of the language, and cannot be divorced from any aspect of it. These initial changes to words are as integral a part of Welsh as, say, the endings to words are in German or Russian." *
If however, you are determined to master the rules early on in your studies we have listed them below. We have highlighted perhaps the most commonly applied mutation rules in each class should you decide to start with these first.
1. When the definite article ( y before a consonant or yr before a vowel) is used before a feminine noun the noun undergoes a soft mutation (this rule does not apply if it begins with ll- or rh- ).
When using the article before a masculine noun, soft mutation does not occur.
When using the article before a feminine noun, soft mutation occurs.
e.g. merch = girl ( n.f. ) Mae'r ferch wedi seiclo yma. - The girl has cycled here.
2. Adjectives which follow feminine nouns also undergo mutation.
e.g. tal = tall Mae'r ferch dal wedi seiclo yma. = The tall girl has cycled here.
3. Most Welsh prepositions require a soft mutation. See list below:
dros y penwythnos = over the weekend
dros benwythnos = over a weekend
4. The possessive pronouns 'your' (singular, familiar) = dy.....(di) and 'his' = ei...(e/o) require soft mutation.
llaw = hand
ei law...(e/o) = his hand
troed = foot
dy droed....(di) = his foot
Ei also means 'her', but when so used it requires an aspirate mutation. (see below)
1. A nasal mutation occurs after use of the preposition yn (in). Yn does not cause mutation when used as a particle before a verb.
2. A nasal mutation also occurs after fy . The word fy (my), causes nasal mutation in the words listed below:
dillad - clothes
brawd - brother
tadau - fathers
fy nillad - my clothes
fy mrawd - my brother
fy nhadau - my fathers
Sometimes, in the spoken language, fy is omitted entirely.
1. After "a" a is the Welsh word for and ( ac is only used before vowels, hence it cannot cause an aspirate mutation).
* Gareth King: Modern Welsh A Comprehensive Grammar p. 13