Two very nooby Irish questions
Firstly, what is the difference in usage of "Tá" and "Is", and when are they used?
Secondly, what is the difference in usage of "Níl" and "Ní", and when are they used?
Please someone help me with these 2 problems, as I've been struggling with them as long as I've known them.
I'm still a noob, and this is how I try to remember the difference in my current noob stages (someone correct me if I'm wrong so far):
When you want to say:
(1) "Noun" is "noun", or "pronoun" is "noun" or vice-versa, use Is (which is ní in negative, and an in a question)
(2) "Noun"/"Pronoun" is "adjective"/"at location x"/"at time x" etc., use Tá (which is níl in negative, and question word an (not the same "an" as above) + bhfuil in a question)
Look at the recent discussion scilling linked as well, and try to check every discussion where the verb bí and the copula are used, very often people ask similar questions or clarifications, and a lot of useful tips and examples are hidden in those.
Examples (hope I got those right):
(1) "It is an apple", you compare "it" with "apple", therefore
Is úll é. Ní úll é. An úll é?
(2) "The apple is in the fridge", you specify the location of the apple, therefore
Tá an t-úll sa chuisneoir. / Níl an t-úll sa chuisneoir. / An bhfuil an t-úll sa chuisneoir?
The next tricky part in the duolingo tree comes with the question words (as Knocksedan mentions, some of them have an embedded copula), and how to order the nouns and pronouns, and which pronouns to use with the copula.
I think it's easier to break it down in small pieces with simple statements, so that's why I shared you my first "trick" without mentioning the other aspects.
I'm at the part where I still scratch my head with some of the question words, but I think I got the pronoun madness under control now -- thanks to our very helpful duolingo friends scilling, Knocksedan, and galaxyrocker, who all give advice in almost every discussions in the Irish forums ;)
I would like to second your statement about Knocksedan, scilling and galaxyrocker, their input and explanations are invaluable. It literally means having access to tutors; i get most of my queries answered by searching the forum for their comments. Duolingo ought to give them some sort of award - or reward would probably be more appropriate.
Unfortunately no matter how many times I read that discussion it seems to go over my head. Is the copula form used ONLY in the cases mentioned or are there other cases?
The basic form of the copula in Irish is the equivalent of "noun is noun" in English. The structure can change slightly (X is the Y, A X is a Y, The X is a Y) and many of the "who, what, why, where" type questions also use the copula, but the place to get started is to remember that you say tá sé fuar, but is fear é, because fuar is an adjective, and fear is a noun.
Níl and Ní is even simpler, (though it does help to recognize when the copula is used).
Ní is the negative participle used to negate present tense verbs - ní rithim, ní léann sí an leabhar, ní ólaimid beoir. The twist, though, is that the verb Bí, which uses the form tá in the present tense, uses a different form after the interrogative and negative participles - an bhfuil and ní fhuil, except that ní fhuil has collapsed to níl. So Níl is only ever used when the positive form of the sentence would be tá. If the positive form of the sentence uses anything else except Tá, you use Ní.
The difference between tá and is is the same as between ní and níl. At the very basic, look at what you're using. If there are two nouns or a noun and a pronoun, use is or ní. Otherwise use tá or níl (which is merely forms of bí)