| Letter Llythyren | Soft Meddal | Nasal Trwynol | Spirante Llaes |
| P | B | MH | PH |
| T | D | NH | TH |
| C | G | NGH | CH |
| B | F | M | |
| D | DD | N | |
| G | - | NG | |
| LL | L | ||
| M | F | ||
| RH | R |
Treiglad meddal. Soft mutation occurs:
- in the female names, after y, yr, `r, or un:
cath / y gath, un gath ; merch / y ferch, un ferch
- at the beginning of all the names, after dau and dwy
- at the beginning of the adjectives following a singular feminine noun:
cath + tew / cath dew
- at the beginning of the verbs that start a question:
taloch chi / daloch chi ?
- at the beginning of the verbs (expect those starting with P, T or C) that start a sentence in the negative:
bwytais i / fwytais i ddim
- at the beginning of the names or adjectives after the particle yn:
tew / mae Ffred yn dew
There are no mutations in the verbs:
mae Ffred yn mynd
- after the possessives dy (yours) and ei (his):
pen / dy ben di ; car / ei gar e
- at the beginning of the names that are direct complements of the verb in its short form:
rhaglan / gwelais i raglan
- after the prepositions am, ar, at, dan, dros, drwy, heb, hyd, gan, wrth, i, o:
Llanelli / dw i'n dod o Lanelli
Treiglad trwynol. Nasal mutation occurs:
- after the possessive fy (my):
car / fy nghar i
- after yn (preposition meaning “in“):
Caerdydd / yng Nghaerdydd
Treiglad llaes. Spirant mutation occurs:
- after a (and):
coffi / te a choffi
- after the possessive ei (her):
pen / ei phen hi
- at the beginning of the verbs beginning with P, T or C beginning a negative sentence:
talu / thalais i ddim
- after na (than):
coffi / mae te 'n well na choffi