"The metro station."
Translation:An stáisiún meitreo.
The genitive in English for “X” is generally expressed either by “X’s”, “Xs’”, or “of X”. Stáisiún an mheitreo (presuming that that’s the genitive form for meitreo) would mean “the metro’s station”, and ríomhaire na leabharlainne would mean “the library’s computer”. In my view, the latter makes sense in the genitive — more sense than it does as an adjective in “the library computer” — but the former doesn’t, since I’d expect meitreo to be an adjective. However, this perhaps is reflective of my mother tongue being English, and because “metro” in “the metro station” is an adjective rather than a genitive noun.
focloir.ie, uses "stáisiún na traenach" for "the railway station" https://www.focloir.ie/en/dictionary/ei/he+met+me+off+the+train
I have a limited imagination (and never ever understood any grammar), so just to confirm: In the genitive section similar examples were "school work" and "dog food". Would in these cases "school" and "dog" be adjectives, like "big" and "yellow"?
(teanglann didn't know meitreo: I woud have looked for the genitive there.
In English, the “school” in “school work” and the “dog” in “dog food” are adjectives, despite being most frequently used as nouns. In Irish, the scoile in obair scoile and the madra in bia madra are genitive nouns — literally “work of school” and “food of dog” (or “school’s work” and “dog’s food”) respectively. English is more flexible in allowing nouns to function as adjectives than Irish is; Irish colloquially uses the genitive more than English does. One might be able to say obair scolaíoch (“scholastic work”) or bia cainíneach (“canine food”) to specifically use adjectives in Irish, but they’d probably sound somewhat awkward for the purpose, like their English equivalents.
I tried your answer too. This is actually a very fraught question, and native speakers disagree sometimes vehemently about when these compound noun constructions are available (they're not actually adjectives, but whatever). I've never heard "an stáisiún meitreo" from a native speaker, but I've heard "an tiománaí bus" and it almost started a fistfight.