"It is another sandwich."
Translation:'S e ceapaire eile a th' ann.
EDIT: I have written much longer and more comprehensive Guide to Gaelic to be, the substantive verb bi, tha & the copula is now – you might want to read it instead. :)
Because it’s not a grammatically valid sentence that would make any sense in Gaelic.
You cannot use a noun phrase (and ceapaire eile another sandwich is a noun phrase) as a predicate of the verb bi (whose present-tense form is tha).
Gaelic has two different to be verbs, with their own separate uses and you cannot use one when the other is needed:
- bi (with forms: tha, (bh)eil, bha, robh, bidh, etc.) – so called the substantive verb; used to describe things and state their whereabouts. It takes only adjectives, adverbs, and prepositional phrase as its predicates.
- is (bu in the past and conditional) – the copula, used to classify (define) and identify (equate) things. It may take noun phrases as its predicates (but also many other grammatical creatures in many idiomatic phrases, we’ll not look at them right now).
So you use tha, bha, etc. to describe something or say where it is, how it is, when it happened, etc.:
- tha an ceapaire blasta the sandwich is tasty, here an adjective – blasta tasty – is the predicate;
- tha an ceapaire air a’ bhòrd the sandwich is on the table, here a prepositional phrase – air a’ bhòrd on the table – is the predicate.
But when a noun phrase (like ceapaire a sandwich) is the predicate itself, you need either the copula is or some other idiomatic construction with a different structure.
You always use copula if the predicate is definite:
- is mise Calum I am Calum, the predicate is a definite noun – Calum – the copula is used directly;
- ’s e an ceapaire agam it is my sandwich, the predicate again is a definite noun phrase – an ceapaire agam the sandwich of mine, my sandwich;
and in an older poetic language (but not used nowadays in regular conversation) with indefinite nouns:
- is ceapaire e it is a sandwich,
- is tidsear me I am a teacher.
And commonly you use other periphrastic structures with indefinite nouns:
- ’s e ceapaire a th’ ann it is a sandwich, but literally: it’s a sandwich that is in it – notice that a prepositional phrase ann in it is the predicate of tha, not a noun;
- ’s e tidsear a th’ annam I am a teacher, but literally: it’s a teacher that is in me – again a prepositional phrase annam in me is the predicate of tha;
- tha mi nam thidsear I am a teacher, but literally: I am in my teacher – here we use only the tha verb, but again the predicate is a prepositional phrase nam thidsear in my teacher;
That’s why the only grammatical ways to say it is another sandwich are:
- ’s e ceapaire eile a th’ ann (it’s another sandwich that is in it),
- tha e na cheapaire eile (it is in its another sandwich) – but this one’s sounds a bit odd to me here – but I’m not a native, so not sure – probably not the best choice – I’d stick to this construction rather to state people’s occupation,
- is ceapaire eile e (it is another sandwich) – the most straightforward but also very poetic/archaic, so not used in regular conversation (and I don’t think accepted by Duolingo).
If you’re looking for a book, Scottish Gaelic in Twelve Weeks by Roibeard Ó Maolalaigh is pretty good. Don’t let the title discourage you – it sounds a bit like a cheep self-learning thing but it’s actually a quite good and fairly comprehensive (especially for a beginner textbook) grammar book with exercises and some reading texts.
Also Colin Mark’s Gaelic Verbs Systemised and Simplified is good for verb tables and a lot of example sentences with translations (but that one’s for verbs only).
Also, for tha and is – check out my much longer guide linked above. :)