"Sioned will go to work on the train tomorrow afternoon."
Translation:Gwnaiff Sioned fynd i'r gwaith ar y trên prynhawn yfory.
I think this is idiomatic in Welsh in expressions like "i'r ysgol", "i'r eglwys", "i'r gwely". Maybe we should rather ask why the definite article is idiomatically omitted in English in the equivalent expressions. Someone please correct me if I am wrong. Or perhaps there is a better explanation.
Can I add a point here? After thinking a bit about it, I have the impression that, in cases where in English we omit the definite article, it is because the noun doesn't really mean a place, but rather an activity. This is obvious with "work" because the work in question could take place in all sorts of different places. We would say we are "going to bed" even if we sleep in a sleeping bag on the floor. We would say we are "going to chapel" if it is to worship, but "to the chapel" if we are going to clean the place! A hospital nurse would not say say "I went to hospital at seven o'clock this morning," but "to the hospital." I wonder if I am clarifying things or making them more obscure?
Indeed! We go "to the office" and "to the supermarket" and "to the post office" and "to the bank", so why not "to the work, to the school, to the bed"? Turns out some other languages (such as Welsh) do just that!
I agree that English is the one that needs to be explained here.
(And sometimes even English is inconsistent, e.g. UK "was taken to hospital" / US "was taken to the hospital".)