A subordinate clause depends on another clause called the main clause. The subordinate provides information within a larger structure and does not appear alone with complete meaning. In Spanish, it is marked with connectors or forms that link it to the main clause.

The typical structure is a main clause plus a connector plus a subordinate clause. The subordinate can go after, before, or, with some twists, inserted in the middle. The dependency remains because the subordinate fulfills a function within the main clause.

Connectors are words or groups that introduce subordinate clauses and indicate their type. The most frequent are that, if, who, where, how, when, and so that. Each connector is typically associated with a type of meaning.

A noun-subordinate clause functions as a noun within the main clause. It can be the subject, direct object, or complement of a noun, an adjective, or a noun phrase. In Spanish it is usually introduced by que or si in constructions such as doubt.

A relative clause describes or identifies a noun and is equivalent to an adjective. It is also called a relative clause and is usually introduced by que, quien, el cual, cuyo, donde or como. Within the relative clause there is a reference to the antecedent, sometimes omitted for economy.

Adjective (relative) clauses can be restrictive or explanatory. Restrictive ones select a subset and do not use commas; explanatory ones add information and are set off with commas. Punctuation changes the meaning and interpretation of the antecedent.

An adverbial subordinate clause expresses circumstances such as time, cause, purpose, condition, concession, or manner. It functions as an adverbial complement of the main clause. It is introduced with specific connectors according to meaning.

In subordinate clauses, the indicative is used for facts or with a factual value, and the subjunctive is used for desire, doubt, evaluation, purpose, or undefined existence. The choice depends on the sense of the main clause and the connective. Many subordinate clauses with que alternate between indicative and subjunctive depending on meaning.

When the subordinate clause comes first, it is typically followed by a comma before the main clause. Explanatory clauses are set off by commas around the subordinate clause. Initial conditional and temporal clauses are usually marked with a comma to clarify the boundary.

To use subordinate clauses in Spanish, choose the type of information you want to add, select the appropriate connector, and adjust the verb mood according to the sense. Maintain punctuation to distinguish restrictive and explanatory clauses. Clarity depends on respecting the dependency between the main clause and the subordinate clause.