Cláusulas subordinadas: visión general

A subordinate clause is a clause that depends on a main clause to make a complete sentence. Quiero que vengas is one sentence built from two clauses: the main quiero and the subordinate que vengas. El libro que compré ayer es bueno embeds que compré ayer inside the main el libro es bueno. Cuando llegues, llámame uses cuando llegues as a temporal modifier of llámame. Three different subordinate clauses, three different jobs.

Spanish classifies subordinate clauses by the grammatical role they play in the main clause. There are exactly three families: substantive (noun-like), adjective (modifier of a noun), and adverbial (modifier of a verb). Each family has its own set of introducing words, its own mood-selection rules, and its own dedicated grammar pages elsewhere on this site. This page is the map: it shows you the three territories, the routes between them, and the master rule that decides indicative versus subjunctive in each.

If you understand this page, every individual subordinate-clause page you'll encounter later — cuando with subjunctive, aunque with mood alternation, the relative pronouns — fits into a clear taxonomy. You can predict the mood. You can identify the role. You can debug your own errors.

The three families

The same surface word (que, for instance) can introduce two completely different things: Quiero que vengas (substantive: object of quiero) and El libro que compré (adjective: relative modifying libro). The way to tell them apart is to ask what grammatical role the clause plays in the main sentence.

Family 1: substantive clauses

A substantive clause stands in for a noun. It can be the subject, the direct object, or the complement of a preposition. Spanish substantive clauses are introduced by que (for declarations) or si (for embedded yes/no questions).

As object

In each case, the que-clause is what the main verb takes as its object: quiero [que vengas], sé [que no es fácil], no creo [que tenga razón]. You can replace the clause with eso and the sentence still works: quiero eso, sé eso, no creo eso.

As subject

Here the que-clause is the subject of the main verb. The structure is the impersonal es importante [que llegues]… — what is important? — [que llegues a tiempo]. The clause fills the subject slot.

With si — embedded yes/no questions

When the embedded clause is itself a yes/no question (a hypothetical "yes or no"), Spanish uses si instead of que. The two are not interchangeable: Sé que viene asserts that she's coming; no sé si viene asks whether she is.

Mood in substantive clauses

This is where Spanish substantive clauses get tricky. The mood inside the que-clause depends on what kind of meaning the main verb expresses:

• Volition, emotion, doubt, possibility, denial → subjunctive in the subordinate clause.
  • Quiero que vengas (volition).
  • Me alegra que estés aquí (emotion).
  • Dudo que sea verdad (doubt).
  • No creo que llueva (denial / disbelief).
• Assertion, perception, knowledge → indicative in the subordinate clause.
  • Sé que es verdad (knowledge).
  • Veo que estás cansado (perception).
  • Creo que llueve (assertion of belief).

The underlying logic: the subjunctive marks content that the speaker is not asserting as real. Wishes, doubts, denials, evaluations — none of these assert the embedded content as true. The indicative marks content the speaker treats as real or known. Once you internalise this, you can predict the mood in clauses you've never seen.

Negation flips the mood because it flips whether the speaker is asserting the embedded content. The whole subjunctive system is built on this asserted/non-asserted distinction.

Family 2: adjective (relative) clauses

An adjective clause modifies a noun, the way an adjective does. The noun being modified is called the antecedent. The clause is introduced by a relative pronoun — que, quien, el cual, donde, cuyo.

The relative pronoun's choice depends on the antecedent: que for things and people in most contexts, quien for people in formal or prepositional uses, donde for places, cuyo for possession ("whose"). For time antecedents, peninsular Spanish uses en que / en el que (el verano en que nos conocimos) — not bare cuando, which is dispreferred as a relative pronoun in modern usage.

Mood in relative clauses

Relative clauses use the indicative when the antecedent is specific and real, and the subjunctive when the antecedent is non-specific, indefinite, or non-existent.

The subjunctive in relative clauses signals "I'm describing a set of properties, not pointing at a specific instance." This is the same speaker-stance logic as substantive subjunctives: when the content isn't asserted to refer to a real instance, the subjunctive marks it.

Family 3: adverbial clauses

An adverbial clause modifies the main verb, the way an adverb does. It tells you when, why, under what condition, despite what, for what purpose, or how something happens. Adverbial clauses are introduced by a wide variety of subordinating conjunctions, grouped by semantic function.

Subtypes and their conjunctions

Each subtype is covered in detail on its own page; see the related-pages list. The map above shows you what's out there.

Example sentences across the adverbial families

Mood in adverbial clauses

This is the most complex of the three families. The mood depends on the conjunction and on whether the content is presented as real/established or as hypothetical/anticipated.

Three groups by mood behaviour:

Always indicative (presented as established fact):

• porque, ya que, puesto que, dado que, como (causal — the cause is real)
• así que, de modo que, de manera que
  • indicative when expressing real consequence

Always subjunctive (purpose, anticipation, condition that hasn't happened):

• para que, a fin de que, con el objeto de que (purpose)
• a menos que, salvo que, con tal de que, en caso de que (conditional alternatives)
• antes de que (anticipation)
• sin que (manner of non-occurrence)

Mood alternation (depends on whether the content is real/past or hypothetical/future):

• cuando, mientras, en cuanto, hasta que, tan pronto como — indicative for habitual or past, subjunctive for future or anticipated.
• aunque, a pesar de que — indicative if the content is acknowledged as real, subjunctive if it is hypothetical or downplayed.
• si — indicative for real conditions, imperfect subjunctive for counterfactual conditions.

A unifying rule across all three families

The mood-selection logic is the same across substantive, adjective, and adverbial subordinate clauses, even though it looks like three different sets of rules. The unifying principle:

The subjunctive marks content that the speaker is not asserting as real, established, or specific.

• In substantive clauses: subjunctive after volition/emotion/doubt (the embedded content isn't asserted).
• In adjective clauses: subjunctive when the antecedent is indefinite or non-existent (the antecedent isn't asserted as a real instance).
• In adverbial clauses: subjunctive for anticipated/future/hypothetical events (the event isn't asserted as having happened).

In every case, the indicative says "this is the way things are/were"; the subjunctive says "this is what I want, doubt, hope, anticipate, or describe abstractly." Spanish grammar pages will give you long lists of conjunctions and verbs that "trigger" subjunctive, but you don't need to memorise the lists if you understand this principle — the lists fall out of it.

Same word, different family: que

The word que introduces substantive and adjective clauses. To tell which, ask what the clause is doing.

In the first, que viene mañana is what I know — the clause is the object. In the second, que viene mañana tells you which chica — the clause modifies the noun.

A practical test: can you ask ¿qué? and have the clause as the answer? If yes, it's substantive. ¿Qué sé? — Que viene mañana. For the adjective version, that test fails: ¿qué viene mañana? doesn't answer cuál chica.

Same word, different family: donde

The word donde introduces adjective clauses (modifying a place noun) and adverbial clauses (modifying a verb).

Both are subordinate clauses, both use donde, but they're in different families. The adjective version requires an antecedent noun (el pueblo); the adverbial version stands alone. (Note that cuando — unlike donde — is rarely used as a relative pronoun in modern peninsular Spanish; with a time-noun antecedent, use en que / en el que instead.)

Same word, different family: si

The word si introduces substantive (embedded yes/no question) and adverbial (conditional) clauses.

In the first, si vendrá is the object of sé. In the second, si viene is the condition under which the main clause holds. The mood behaviour also differs: substantive si takes the indicative; adverbial conditional si takes the indicative for real conditions and the imperfect subjunctive for counterfactuals.

English contrast: the that and which family

English uses that for both substantive (I know that she's coming) and restrictive relative (the book that I bought). English also has which (non-restrictive), who (people), where (place), when (time), and so on. Spanish has a similar split, but with one major divergence: Spanish requires the relativising word even where English drops it.

The pattern: where English allows zero subordinator, Spanish requires que (or another relativiser). Forgetting it (❌el libro compré ayer) is one of the most frequent A1/A2 errors from English speakers.

How to navigate the rest of the grammar

This page is the map. The territory is on the individual pages:

• For substantive clauses → the subjunctive uses page and its sub-pages on verbs of volition, emotion, doubt, etc.
• For adjective clauses → the relative-pronoun pages: relative-que, relative-quien, and others.
• For adverbial clauses → the dedicated pages on temporal, conditional, concessive, causal, and purpose clauses (each with its own mood rules).

When you encounter a confusing subordinate clause in the wild, run it through the three-question diagnostic:

1. What family is it in? (Substantive, adjective, or adverbial?)
2. What introduces it? (Which conjunction or relative pronoun?)
3. Is the content asserted as real, or as hypothetical/anticipated/indefinite?

Those three questions narrow down the mood, the form, and the meaning in almost every case.

Common Mistakes

Key takeaways

• Three families of subordinate clauses: substantive (act as nouns), adjective (modify nouns), adverbial (modify verbs).
• Each family has its own introducing words but the same underlying mood logic: subjunctive for unasserted/hypothetical/indefinite content; indicative for asserted/real/specific content.
• Substantive que-clauses take the subjunctive after verbs of volition, emotion, doubt, denial; indicative after assertion, knowledge, perception.
• Adjective (relative) clauses take the subjunctive when the antecedent is non-specific or non-existent.
• Adverbial clauses split into always-indicative (causal), always-subjunctive (purpose, condition, anticipation), and alternating (cuando, aunque) groups.
• The same word (que, cuando, si) can introduce different families. Identify the role to identify the family.
• Spanish requires que even where English drops that — sé que viene, never ❌sé viene.