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This resource is provided by AmeriCymru and is intended for Welsh learners who are not yet ready to commit to a full time course. With Croeseiriau Cymraeg you can devise your own schedule and learn at your own pace. Before you start please go to this page: Croeseiriau Cymraeg and read the 'Introduction' and 'How to Use' sections.

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  • Possible Mutations

    First Letter

    p t c b d g m ll rh

    Soft Mutation

    b d g f dd omit g f l r

    Nasal Mutation

    mh nh ngh m n ng - - -

    Aspirate Mutation

    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.

    Soft Mutation


    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.

      e.g.  bachgen = boy ( n.m. )  Mae'r bachgen wedi seiclo yma. - The boy has cycled here.

      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:

                   am - ar - at - dan - dros - drwy - gan - heb - hyd - i - o - wrth


       dros y penwythnos = over the weekend  

       dros benwythnos = over a weekend

       The Welsh word for course is cwrs . The Welsh phrase for 'of course' is wrth gwrs . Note the soft          mutation.

       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)


    Nasal Mutation

    180px-Exclamation_encircled.svg.png 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. 

    Aspirate Mutation


    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

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