This bit of grammar been at me for years, would like some help clarifying when to use which one. Here is an example: Atá tú A bhfuil tú What is the difference and when can you use which?
Different relative clauses
X atá tú, direct relative clause, X is subject or object of the relative clause (both impossible here. There’s no object of tá and it’s subject must be tú here.) or predicate of a cleft sentence e.g. Is ag scríobh ata tú, Is ann atá tú
X a bhfuil tú [color=red]in[/color]direct relative clause. A resumptive pronoun in the relative clause is referring back to the antecedent X , e.g. an sliabh a bhfuil tú air = the mountain on which you are, an file a bhfuil tú ag léamh a leabhair = the poet whose book you’re reading, Or there’s an adverbial relation. e.g. an áit a bhfuil tú = the place where you are
In many cases, the use of “atá tú” or “a bhfuil tú” depends on the question word preceding it. For example, “conas” is followed by a direct relative clause (atá tú), whereas “cén chaoi” is followed by in indirect relative clause (a bhfuil tú). Which is why you get “conas atá tú”, but “cén chaoi a bhfuil tú”. The list could be extended, of course.
Yes, I definitely recommend reading about the subject of direct relative vs. indirect relative, as it affects how the verb is treated regardless of whether it is a form of “bí”, the copula, or any other verb.