The article analyzes Estonian purpose clauses on a typological background. In Estonian, there are three kinds of purpose clauses: (1) clauses expressing the desired result of intentional action, (2) clauses expressing a function for the fulfilment of which somebody or something is necessary/unnecessary or appropriate/inappropriate, and (3) clauses expressing either a hidden purpose or, rather, a consequence and temporal succession.
The Estonian purpose clause is, by form and by content, closely connected with the complement clause as well as with the adverbial clauses of reason and result. Its similarity now with the clause of reason, now with that of result is probably due to its simultaneous expression of both reason and result (the reason as well as the expected result of the action described in the main clause).
A purpose clause with a da-infinitive as main verb is referentially dependent on the main clause. The obligatory omission of its subject is controlled by a member of the main clause, mostly the actor, but possibly also the undergoer (the beneficiary of the main clause or, in the case of an impersonal main clause, the total object). If the purpose clause is in the conditional mood, the clause is referentially independent of the main clause and it can be used regardless of whether its subject coincides with any argument of the main clause or not.