A subordinating conjunction (conjuncion subordinante) connects two clauses that are not equal in grammatical status: One clause is the main clause that can stand alone while the other is a subordinate clause that depends on the main clause for full meaning.

Subordinating conjunctions mark the dependent clause, which means the clause can appear before or after the main clause without a change in meaning, although the emphasis or tone of the sentence might change slightly. When the subordinate clause comes before the main clause, a comma must separate it from the main clause, but when the main clause comes first, no comma is needed.

Subordinating conjunctions express different relationships between clauses:

These subordinating conjunctions introduce a dependent clause that expresses the cause or reason for the main clause. For example:

This group indicates the result or consequence of the action in the main clause. For example:

"Si" is the most common conditional conjunction which introduces a condition that must be met for the main clause to happen. Other conditional conjunctions, such as a menos que, a no ser que, con tal de que, en caso de que, etc. are used in unreal conditionals which trigger the subjunctive mood. For example:

These conjunctions add information about when the action in the main clause happens. They require the use of subjunctive in the subordinate clause when they refer to future actions. For example:

They indicate the intention or goal behind the main clause. They always take the subjunctive in the dependent clause. For example:

These conjunctions express concession or contrast between the two clauses. They require the subjunctive when they express an assumption or hypothesis in the dependent clause. For example:

These conjunctions introduce clauses that compare the degree, manner, or quantity of the action in the dependent clause with the main clause. For example: