"To drink too much"
My guess was yfed ormod with gormod softly mutated since it's an adverb, but Duo says it's yfed gormod.
Can yfed ormod also be used? Or yfed yn ormod?
yfed gormod is correct. gormod exists as both an adjective (excessive, say) and as a noun (an excess, plural gormodion):
- yfed gormod - drinking an excess = drinking/to drink too much
yn ormod would work, too, in conjunction with a verb:
- Mae Hefin yn yfed yn ormod - Hefin is drinking excessively/to excess/too much
And we can also be more specific:
- Dych chi wedi yfed gormod o ddŵr/gwrw/sudd/[laeth/lefrith]/goffi... - You have drunk too much water/beer/juice/milk/coffee...