Translation:Do they use the euro in Germany?
"an úsáideann siad" - Is this how you would say it in Irish or would you use autonomous? I'm still not clear what exactly that's used for.
One would use the Irish sentence as it stands if “they” refers to a particular group of known people rather than to people in general.
I don't really like "usaid" as a verb. I'd prefer something like "An bhfuil an euro i bhfeidhm sa Ghearmain?" or the like.
So are all the countries that are preceeded by an always lenited? Or only in certain circumstances?
Grammatically feminine nouns are lenited after "an", and lenite any following adjective you might want to use. They all seem to be feminine except Sasana, Ceanada and Meiriceá, which also aren't preceded by "an".
Is it gramatically incorrect in English to say "they use euro in Germany" (without the)?
While many (most?) people in Ireland use "Euro" as a plural, non-Euro-zone English speakers in the UK and the USA tend to say "euros", so they would say "they use euros in Germany".