"We had a good party but we had wet weather too."
Translation:Gaethon ni barti da ond gaethon ni dywydd gwlyb hefyd.
Why does "da" not lenite when "parti" does? I thought adjectives lenited if the noun they are describing did.
parti has caught the 'object of a conjugated verb' mutation and does not pass it on.
If we were describing a chair (cadair), say, then any adjectives following the feminine noun cadair would all mutate:
- Roeddwn i'n hoffi y gadair goch fawr oedd yn y 'stafell 'na. (I used to like the big red chair that was in that room.)
Okay, but why does this rule not apply for dywydd? It is in the same position as barti.
Your dywydd is a lenited tywydd, so the rule does apply -- it is lenited just as parti was to barti.
(And it's tywydd gwlyb rather than tywydd wleb since tywydd is masculine - at least according to the Bangor and Trinity St David dictionaries. GPC has it as either masculine or feminine.)