"Dw i wedi aros yn y gwesty bedair gwaith."

Translation: I have stayed in the hotel four times.

[sbnaidu]

1. Do you use pedair for time (instead of pedwar)
2. Why do you mutate pedair?

[ibisc]

1. Yes - gwaith (time, occasion) is feminine, so we must use the feminine form of four pedair with it

2. Here, pedair gwaith is an adverb of time, so it gets a soft mutation.

[iAmOnDuolingoToo]

Why does "gwaith" drop the G in "unwaith" and "dwy waith" but not in "pedair gwaith"?

[ibisc]

As in the previous post, gwaith with this meaning is feminine (gwaith 'work' is masculine).

un causes soft mutation of feminine nouns, and both dau/dwy cause soft mutation in all nouns.

pedair, the feminine form of pedwar, causes no mutation.