"I have gone to school today."
Translation:Dw i wedi mynd i'r ysgol heddiw.
Why do you have to use "i'r" here when there's no "the" in the english sentence?
English is inconsistent in its use of the definite article in going to a specific location, eg 'to the office', 'to the shop', 'to the pub' but 'to school', 'to work'. In the latter two the underlying meaning is 'to (the) school' and 'to (the place of) work.
Welsh is more consistent and uses "i'r" (to the) for all of these situations.