Why 'dylen nhw fod' and not 'dylen nhw bod'?

Could someone please tell me what triggers the mutation of bod in this instance?

I can’t give the proper explanation but after o,hi, i, ni, chi nhw etc there seems to be a mutation.

Eg i want you to finish

Dwi isio i ti orffen

You should feel proud

Dylet ti fod yn falch


edit just realised this is rubbish sorry!

Could be that ‘W’ is a vowel in welsh (but grammar is far from a strong point for me).

Cheers J.P.

The conditional tense (should, could, would*) cause a soft mutation - not the pronoun (nhw, ti, fi etc.)

Dylwn i fod
Dylen nhw fod
Dylai hi fod

Gallwn/Medrwn i fod
Gallen/Medren nhw fod
Gallai/Medrai hi

I have * would - because would in a pure sense uses “yn”:
Baswn/Byddwn i’n mynd - I would be going = I would go. (Can’t say Baswn i’n bod - I would be be)
Basen/Bydden nhw’n mynd
Basai/Byddai hi’n mynd

But I would like:
Hoffwn i fod
Hoffen nhw fod
Hoffai hi fod

It’s the verb that cause the mutation. “Bod” doesn’t cause it - (dw i’n, baswn i’n, bydda i’n, ro’n i’n)


I should add this is what happens whenever the mutation happens with a verb:

Past tense (not bod):
Wnes i weld car - I saw a car
Welais i gar - I saw a car

Ro’n i’n gweld car - I was seeing a car

Present tense (Bod):
Dwi’n gweld car - I am seeing a car / I see a car

Present tense (not bod):
Ga(f) i weld car? - May I see a car?
Galla(f) i weld car - I can see a car

Future tense (Bod):
Bydda(f) i’n mynd gweld car - I will be going to see a car

Future tense (not bod):
Gwna(f) i fynd i weld car - I will go to see a car

Does that make sense? It’s not the pronouns.


Thanks guys. I wasn’t sure if ‘nhw’ was one of the miscellaneous words such as ‘ei’ or ‘dy’ that cause mutation or the tense. Much appreciated.


I thought it was the “I, he, she, you, them” words that cause the mutation. The “yn” in the “bod” structures protects from the mutation.

I’ll make a better explanation later when I’m not stirring a curry. :blush:


It’s the same with “gan” and “ar” - they both cause the mutation. So “Mae gynno fo gar” and “Mae ganddo gar” both form the soft mutation without the pronoun “fi, fo, hi, nhw…ayyb”.

You don’t always have to include the pronoun in a sentence “Darllenais lyfr” - I read a letter. But the treiglad still occurs.

Also, words like “mor” don’t mutate: mae hi mor dal â fi

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Me too but what about

Ddudes i bo fi ddim isio nhw.

Lets just go with…don’t worry about it!

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“bo’ fi” is colloquial, so it doesn’t follow the patterns. In written Welsh: Ddywedais i fy mod i ddim…

However, if remembering the treiglads by thinking about them in these terms works then go for it!! It works and keeps you talking. It’s not worth stressing about. If you want to write Welsh, then maybe think about it, but don’t stress :slight_smile:


But the pronoun should be there (even if we voluntarily omit it) so the mutation survives.

I genuinely don’t know …

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Sometimes its more formal to leave it out.

It’s a kinda like this:

Prynais i gar

cause pronoun effect

As I said - mae hi mor dal â fi not mae hi for dal a fi.

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Bo fi I think is a colloquialism … It should be “fy mod i”.


There seem a lot of bo’ fi, bo’ ti etc colloquialisms :wink:

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Like “I’m” and “you’re” really


Exactly…i think its just a case of getting used to them :slight_smile:

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Short forms of verbs (in this case ‘dylen’) cause mutation of the following verb (and also of direct objects)
Wps - what @AnthonyCusack said, really


What about - the object of a short form of a verb.

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A more correct, but possibly flippant, answer is: that’s what everybody does :slight_smile:


I think it’s actually the subject of the verb.

“Dylen nhw bod” - “They should be” - “They” is the subject.

This is a point that Gareth King makes in his “Modern Welsh: A Complete Grammar” book, and has also written about it on here I think, but definitely on forumWales.
(Not everybody agrees with him, but he gives what seems to be a convincing explanation).

I think he says that this is the cause of most soft mutations in Welsh, although of course there are other reasons.

Note that the subject of the sentence is sometimes implied rather than explicitly stated, and this still causes soft mutation, which can look a bit mysterious sometimes.

Here is a forumwales thread about it, in which Gareth joins in, and stoutly defends his view:


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