Bydd ansoddeiriau ac enwau'n treiglo'n feddal ar ôl 'yn traethiadol':

Dych chi’n dda.             (da – good               – adjective – soft mutation)
Dych chi’n berson da.   (person – person   – noun – soft mutation)

Fydd berfenwau ddim yn treiglo ar ôl 'yn traethiadol':

Dych chi’n cwyno gormod (cwyno – verb – to complain – no mutation )

Os na fyddwch chi'n siŵr ai ansoddair yw gair neu beidio, gofynnwch y cwestiwn:

Sut fath o berson yw e / hi?

Os byddwch chi'n gallu dweud y gair fel ateb i'r cwestiwn hwn, wedyn andoddair ydy, e.e:

creadigol – Pa fath o berson yw e? – Mae e’n greadigol
creative – What sort of person is he? – He is creative

Adjectives and nouns take a soft mutation after ‘yn’:

Dych chi’n dda.           (da         - good     - adjective - soft mutation)
Dych chi’n berson da.  (person - person  - noun       - soft mutation)

Verbs do not mutate after ‘yn’:

Dych chi’n cwyno gormod (cwyno – verb - to complain - no mutation )

If you are unsure whether a word is an adjective or not, ask the question:

What sort of person is he/she?

If this question can be answered with the word it’s an adjective, e.g:

creadigol - Pa fath o berson yw e?      -  Mae e’n greadigol
creative  - What sort of person is he? -  He is creative