I think “reiligiúnach” and “reiligiúnda” are just basically variants of the same thing. There might be a slight difference in usage but I wouldn’t get too hung up on that. There are a huge amount of variations of different words in Irish – it’s just something you’ll get used to. Likewise with the other two words. I think they more or less mean the same thing, although searching online I see “naíonra” specifically used to mean a nursery where children are exposed to Irish. I am not sure if this is always the case, but I guess if you’re referring to it with the Irish word, chances are it is an Irish nursery. Not living in Ireland, I can’t say which is the more common term, but when I was in an Cheathrú Rua, I saw at least one sign for a “naíonra” I believe, so that’s about as far as my personal experience goes.
Thanks, Héilics Órbhuí. That’s true, there are lots of variations for the same things in Irish, presumably because of the three main dialects. You’re probably right in thinking there is not much difference. Thanks for your answer.
Based on a quick Internet search, the difference between “naíonra” and “naíolann” seems to be that the former is a “playgroup” (usually an Irish-language one) attended by children for a couple of hours a day, whereas the latter means “crèche” where children are looked after throughout the day. As regards “reiligiúnach” and “reiligiúnda”, I wouldn’t be able to help you, but in many cases Irish uses other words for talking about religion, e.g. “cúrsaí creidimh” (religious matters), “duine cráifeach” (pious/devout person), “leabhar diaganta” (religious book).