Back to trains, and Arriva, I remember arguments online when ATW changed the sign at Llandudno to "Croeso i Gorsaf Llandudno". It felt wrong to me but I don't really know why. Seemed like "i'r gorsaf" or "i'r orsaf" sounded more right, despite "i Gymru" obviously being right.
I'm rambling, apologies. Languages are hard!
One thing that's moving the goalposts on you is that the G in "Gorsaf" (station) is part of the root word, whereas the G in "Gymru" has been mutated from "Cymru".
A soft mutation is triggered after "i" (to), which causes nine letters to change, including c->g, and "g" itself disappears, hence gorsaf->orsaf. So you were right to think that "Croeso i Gorsaf Llandudno" wasn't quite right.* If the "Croeso i" bit wasn't there, then "Gorsaf Llandudno" would have been correct, as mutations can only happen
after particular words.
On the issue of "i" versus "i'r", the first means "to", the second is a contraction of "i yr", which means "to the". In a similar mode to English, you don't need to specify "the" if you're also naming the station: "Welcome to the Llandudno station" doesn't sound right, compared to "Welcome to Llandudno station".
Yes, languages are tricky: just a few years ago, I remember being surprised to learn that German follows a completely different approach to capitalisation of words.
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I recall discussions on "a good name" for the railways of Wales going back
several years on this forum: it's not an easy nut to crack if you want it both bilingual and catchy. The best name I came up with was "Rheilffyrdd Cambria/Cambrian Railways", which would be quite in fitting with the "retro/heritage" names that currently seem to be in fashion, but that could unfortunately be seen as stamping all over a certain heritage railway in Oswestry. Plus the Welsh Government clearly want to form a more encompassing public transport brand, like TfL.
I
am surprised that the "Wales & Borders" name isn't more prominent, after all the promotional material (and franchise-related agreements) suggested it would be. But I don't have much to suggest on that matter other than waiting and seeing if DfT kicks up a fuss (hence why I've not posted anything in-thread before now).
*The mutation of so many place names after "i" causes a headache for sign makers, as if you want to use the popular "Welcome to" (Croeso i) preamble, the placename would mutate after "to", as it does in "Croeso i Cymru". This makes things awkward for places with just one name in both languages (such as Prestatyn or Bangor) as you either have to put the same name up twice (mutated once) or force a mutation into the English, and confuse lots of visitors. A good workaround I've seen is to insert "tref" (town), "pentref" (village), etc. into the preamble, e.g. "Croeso i dref Prestatyn": the word "tref" gets mutated, doesn't cause a mutation in and of itself, and Prestatyn remains unmutated. You can then get fancy and do things like "Croeso i dref Prestatyn welcomes you" over three lines, and so on.