11.4 - Subjunctive-hypothetical clauses
Subjunctive-hypothetical clauses are introduced by the conjunctions tát and áttát. There is no syntactic or semantic difference between the two. They are employed for: 1) hypothetical and concessive (if, although); 2) object clauses, except reported speech. Note, though, that the subjunctive-hypothetical can be used to refer a declaration of will of one's own.
The kind of usage is mainly implied by the verb form employed: the present and past conditional express a condition, respectively possible or impossible, while the other forms imply an object clause instead. The optative is ambiguous, in that it can encode a possible condition which is desired or feared by the speaker, or it can encode a voluntary future in an object clause. This latter possibility is especially common when the speaker is referring a declaration of will of their own.