The soft mutation

The soft mutation is the most common mutation so learn which nine letters change and when.

The following grid shows how the soft mutation works.

Original letterMutated letter
cg
pb
td
g-
bf
ddd
rhr
mf
lll

Some little words use this mutation and there is always a soft mutation after the word for two – dau and the feminine form dwy. The aspirate mutation is used in relation to time and it is used with Hoffwn i..., Dylwn i... and Gallwn i....

This mutation is very commonly used when adjectives follow yn, eg:

  • da: Mae hi’n dda iawn.good: She’s very good.
  • cyfleus: Mae’r dref yn gyfleus.convenient: The town is convenient.
  • tawel: Mae’r ardal yn dawel.quiet: The area is quiet.

When an adjective follows a feminine singular noun, eg:

  • mawr: tref fawrlarge: a large town
  • gwych: ardal wychgreat: a great area
  • cyffrous: ffilm gyffrousexciting: an exciting film

When you use the word Pa? – Which?/What?, you should mutate the word that follows, eg:

  • Pa ferch? – Which girl?
  • Pa faint? – What size?
  • Pa liw? – What colour?

All forms of gan cause a soft mutation, eg:

  • Mae gen i frawd. – I’ve got a brother.
  • Mae ganddo fe/fo feic newydd. – He’s got a new bike.
  • Oes gennych chi gi? – Have you got a dog?

You probably know of other places where the soft mutation occurs. Try to use the soft mutation when you speak and write but don’t be put off if you can’t remember whether something mutates or not. Speak as confidently as possible even if you’re not sure whether you should mutate or not!