I'm trying to make a comparison between possible uses of the copula and the substantive verb in modern Irish versus Old Irish.

I've never thought too hard about it but it occurs to me that both is dorcha an oiche and tá an oiche dorcha are possible in modern Irish (correct me if I'm wrong, there's not usually crossover like this, but both seem natural to me). By comparison Old Irish would have only is dorcha in adaig "the night is dark" (lit. "it is dark the night"), I don't think at-tá in adaig dorcha is possible (again, correct me if I'm wrong).

In any case, there is a clear progression from the Old Irish copula phrase to the modern Irish one, however, where no overt subject occurs modern Irish demands the substantive verb, tá sé dorcha, where Old Irish would use an inflected copula, is dorcha "it is dark". The subject in Old Irish is represented by the inflection of the copula, am dorcha "I am dark", at dorcha "you are dark", he/she/it is dark", etc.

If anybody can correct me on anything I've said so far, I'd appreciate it, but my main concern is the following: Would any of you interpret any semantic difference in modern Irish between is dorcha an oiche and tá an oiche dorcha? Is one more archaic? Is one more common? Is one more poetic, or emphatic? How can the difference be described, or is there any?

I’m no Old Irish expert – but copula is the one thing I read more extensively about, so I hope I’m not spitting nonsense (but I hope someone will double-check my comments anyway).

Old Irish is dorcha in adaig could be interpreted (and if there is no pause, IMO it should) as literally ‘the night is dark’ – it’s a simple VPS sentence – the subject goes at the end (like in Modern Irish), it doesn’t need to be ‘it is dark, the night’ (but of course could – but I think in pronunciation that’d have a pause: is dorcha, in adaig – but of course we cannot know that, as there are no recordings from the 8th century…).

Also, while it’s true you have stuff like am dorcha or am rí, I believe in identification you actually use the 3rd person copula, so stuff like is meise in rí for ‘I am the king; the king is I’ (the pronouns are always predicates in the copular clauses).

There is one thing where in Old Irish you’d actually have to use the substantive verb instead of the copula and make the ‘**tá sé fear’-type sentence – and it’s attested in the glosses – that’s when the predicate of the copula is being fronted, and the subject is a pronoun – so stuff like ‘it is a king that he is’, which in Modern Irish you’d generally express as is rí atá ann. In Old Irish it seems that you’re allowed to use the substantive verb directly here – you can’t use the copula, because ‘that he is’ would be just as, the relative copula form, and it is unstressed, it cannot exist on its own, and you can’t put a pronoun after it because the pronouns are always predicates, not the subjects…

So you’ll see stuff like cía·taí-siu for ‘who are you?’ (as if mod. **cé (a)taoi-se?), is faittech rond·boí-som (as if **is faiteach do bhí (sé)-sean) ‘it is cautious that he was’, is uera pictura ro baí sin ‘it is a uera pictura that that was’ (as if **is uera pictura do bhí sin), etc.

As for modern Irish, I think using the copula is both a bit more literary and also suggest a bit more permanent quality.

Like, I don’t think you’d say, at least traditionally, tá an teach mór, you’d rather say is mór é an teach or is mór an teach (it seems to me that the pronoun was very common here, at least in Munster, when the predicate was an adjective). Because being ‘big’ is not something that happens randomly to a house, it’s just its internal quality. Of course could always rephrase it as is mór an teach é ‘it is a big house; the house that it is, is big’. But I’m not sure if that distinction is really observed in speech these days.

But I think it still works with comparatives and superlatives:

is treise tuath ná tiarna is great ancient knowledge of universal wisdom – that’s how it is, generally, the people are stronger than a lord

but tá tuath níos treise ná tiarna, I believe, feels like a passing comment on the current temporary situation – but maybe just because the seanfhocail actually use the basic copular form so commonly

Yes. There is also "mo cheól thu", as an exception, where the copula is not specifically shown. What is the reason for this? Obviously, it is in grammar books as an exception, but maybe it is not a real copula of identification, just an exclamation????

Ade poses a very interesting question. I would also be interested in knowing how the distinction in use between the substantive verb and the copula evolved. The distinction between the two is something that is not thought properly – if at all – in school.

Some time back, I came across an online article or post that explains the distinction as follows. (I think it was on Reddit but I can no longer find it.) It explained that the substantive verb (Bí) is used to describe situations that are temporary or short-term or where there is a fairly clear end in sight, whereas the copula is used for situations that are long-term, permanent or of indefinite duration or to express qualities that are intrinsic to something (since something intrinsic is essentially permanent).

By way of example, the article contrasted the following two sentences: Tá an fear ciúin. Vs. Is ciúin an fear. These both translate to English as ‘The man is quiet’. However, the first sentence is only making a comment about a particular occasion or moment in time, whereas the second sentence implies that the man is quiet by nature (i.e. that being quiet is intrinsic to his character).

The article also gave as an example the sentence ‘Water is wet.’ Translated into Irish, this would be ‘Is fliuch uisce’. He stated it would be wrong to say ‘Tá uisce fliuch’ since wetness is an intrinsic or permanent quality of water.

I have also seen the following two sentences contrasted (I think on this website). Tá Seán ina mhúinteoir’. Vs. Is múinteoir Seán. The first sentence implies that Seán has only recently become a teacher (such that it is not yet seen as a permanent thing), whereas the second sentence implies that Seán is well established as a teacher.

I also noticed that the substantive verb is used to express possession, whereas the copula is used to express ownership: Tá an leabhar ag Seán. Vs Is le Seán an leabhar. (Ownership can be seen as a more long-term state, whereas possession can be seen as more short-term since you could possess something through borrowing it.)

Apparently, the idea of there being two verbs to be, one for short-term situations and one for permanent situations, is not exclusive to the Irish language. For example, some of the Iberian Romance languages e.g. Castilian, Catalan apparently also exhibit this feature.

When I read that explanation on Reddit (regarding short-term vs. long-term use cases), it was quite a revelation to me and it puzzled me that I had not seen this seemingly fundamental principle explained in any introductory grammar books.

However, I was soon disappointed (or confused) when I realised that the Reddit explanation didn’t quite stand up to scrutiny. Through general reading, I came across loads of examples where the substantive verb was used to describe long-term or permanent situations e.g. (as per Silmeth) ‘Tá an teach mór’, when I would have expected ‘Is mór an teach’. For some reason, all these exceptions seemed to involve the predicate being an adjective or adverb (or adverbial phrase), rather than a noun.

So is it a case that the distinction in use between the copula and substantive verb was originally more clear-cut, and that the substantive verb later (in recent times?) started encroaching on the use cases of the copula (but, for some reason, seemingly only if the predicate was an adjective or adverb or adverbial phrase)? If so, might this be due to the influence of the English language among bilingual speakers? Consider that the English verb Be seems more similar to the substantive verb in Irish (both having a full range of tenses/moods), whereas English doesn’t have an equivalent of the Irish copula. Therefore, maybe there is a tendency to displace the use of the copula through the influence of English.

Btw, some time back, I also came across a website or channel on introductory Irish that – if I remember correctly – explained the difference between the substantive verb and the copula as follows. It claimed that the substantive verb is used when the predicate is an adjective or adverb, whereas the copula is used when the predicate is a noun. (There was no mention of a distinction between short-term versus long-term situations.) I thought that this was a hugely simplistic explanation. But at the same time, I can see how people might be led into drawing that conclusion, due to the substantive verb often being used for long-term situations if the predicate is an adjective or adverb.

Very interesting, Silmeth and Caoilte.

It'd be interesting to know if copula use were declining among younger generations in the Gaeltacht, and also whether there are dialectal differences. Presumably no-one has done research on that.

What about this:
Cad é an t-am é? - what's the time? with the copula.
Tá sé a seacht a chlog - it's 7 o'clock, with the substantive verb.

Isn't it odd that the question has the copula and the answer has "tá"? Although the noun is not the same ("am" doesn't appear in the answer). How does this affect the discussion?

Interesting. This would appear to be an exception to the "rule" in the opposite direction i.e. the copula being used for a temporary situation.

Question words like Cad, Conas, Cathain are all copular words. There are no non-copular equivalents (that I know of). So, in your example, you are forced to use the copula to ask about a fleeting situation (the current time). I'm not sure how to explain that.

(Btw, presumably, you could give a more complete answer: Tá an t-am a seacht a chlog, so that the nouns would essentially be the same in both question and answer.)

Yes. Cad forces the copula. But you could expect "cad é an t-am go bhfuil sé?", although that doesn't seem attested.

As a side observation, in your 'workaround' sentence (cad é an t-am go bhfuil sé), the main clause contains the copula and the subordinate clause contains the substantive verb. (So, you could say that the substantive verb is subordinated to the copula.)

This reminds me of sentences like the following. 'Is fíor go bhfuil tuirse ar Phól faoi láthair.' While Pól’s tiredness might be temporary, the truth regarding his being tired at a particular time will arguably last for ever, so that it makes sense to use the copula in this sentence.

Otoh, my guess is that the following type of sentence, which seems calqued from English, would be regarded as wrong: 'Tá sé fíor go bhfuil tuirse ar Phól faoi láthair'.

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Here's another copular sentence of a similar type, but this time with a noun instead of an adjective for the predicate: 'Is trua gan a thuilleadh long le feiscint uirthi'. (Sentence taken from the recent thread ‘An interesting snippet of Irish text’). The predicate ‘trua’ is used here with the copula, as if to indicate that the relevant pity is a long-term condition.

However, presumably, it wouldn’t be unexpected for a larger amount of ships to appear in the not-too-distant future, in which case, the state of pity would come to an end i.e. this can be assumed to be a short-term condition. So, wouldn’t that suggest that the substantive verb should be used instead of the copula i.e. 'Tá trua ann gan a thuilleadh long le feiscint uirthi'? But I’m not sure if the use of the substantive verb is legitimate in this sentence.

Otoh, it can maybe be argued that the lack of ships at that particular instance is forever associated with pity, such that the pity in some sense lives on indefinitely, thus justifying the use of the copula.

Just another thought. The following three sentences all translate to English as ‘The man is quiet’.

Tá an fear ciúin.
Bíonn an fear ciúin.
Is ciúin an fear.

(Although the middle sentence could also be translated in a more Hiberno-English style as ‘The man do(es) be quiet'.)

The three sentences describe situations that can be likened to the on/off status of a light bulb. The first sentence describes a single instance in time (like when a light bulb is on). The second sentence implies a repeated or intermittent situation (like repeatedly turning on and off a light bulb). The third sentence describes a situation that endures over the long term, without any interruption (like a light bulb that is left on indefinitely).

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The above three-way semantic distinction arguably applies to all [edit: actually only a few, i think] some verbs. Take the verb ‘lie’.

He lies on the couch at this moment. (Although, far more commonly: He is lying on the couch at this moment.)
He lies on the couch whenever he gets tired. (Habitual situation)
Estonia lies to the north of Latvia. (Long-term situation)

For the present tense, English doesn’t distinguish grammatically between the above three situations. (Although, in the case of the past tense, there is a distinct past habitual tense.)

And Irish generally doesn’t distinguish grammatically between these three situations either for the present tense, with the exception is the Be verbs i.e Tá, Bíonn, Is.