"Mae hi'n hanner wedi saith" is wrong without the 'awr' after 'hanner', but "Mae hi'n chwarter wedi deuddeg" is ok. Can someone explain?
Genuine question; why is 'un deg dau' not acceptable? I'm guessing it's a grammatical reason.
No, it is just that the older counting system is usually used for time.
"Wedi ddeuddeg" but "i deuddeg" - can someone explain?
Other way round...
(Once you learn that little ditty there are only another thirty-odd causes of soft mutation left to learn...)