Complex Sentences (Subordination) | Portuguese (Brazil) Grammar

A complex sentence contains a main clause and at least one subordinate clause — a clause that cannot stand on its own and depends on the main clause to make sense. Where coordination links equals (see Compound Sentences), subordination embeds one clause inside or alongside another. Sei que ele veio ("I know that he came") is complex: que ele veio is a passenger that needs the main clause sei to carry it. This is the architecture of fluent, connected speech, and the single most consequential decision it forces on you is mood — whether the subordinate verb is indicative or subjunctive.

The defining test

A subordinate clause fails the stand-alone test. Cover the main clause and ask whether what remains is a complete thought.

Sei que ele veio.

I know that he came.

Strip the main clause and you are left with que ele veio — "that he came" — which is not a complete sentence. It depends on something to introduce it. That dependence is the essence of subordination, and it distinguishes a complex sentence from a compound one, where both halves survive alone.

Brazilian Portuguese has three families of subordinate clause, sorted by the role they play: noun clauses, adjective (relative) clauses, and adverbial clauses.

Noun clauses

A noun clause does the job of a noun — it can be the subject or, far more commonly, the object of the main verb. Most are introduced by que ("that"), and unlike English, this que is never optional.

Eu acho que vai chover.

I think (that) it's going to rain.

Ela disse que chegaria atrasada.

She said (that) she'd arrive late.

In English you can drop "that" — "I think it's going to rain." In Portuguese, omitting que is ungrammatical: Eu acho vai chover is wrong. The que is the structural glue.

Noun clauses are where mood first bites. After verbs of knowing, saying, and perceiving (assertions of fact), the verb stays indicative. But after verbs of wanting, doubting, fearing, and feeling — anything that frames the content as desired, doubted, or emotionally colored rather than asserted as fact — the verb shifts to the subjunctive.

Quero que você venha à minha festa.

I want you to come to my party.

Duvido que ele saiba a resposta.

I doubt he knows the answer.

The subjunctive (venha, saiba) appears because you are not stating a fact — you are expressing a desire or a doubt about something that is not (yet) real. Acho que ele vem asserts a belief about reality, so it is indicative; quero que ele venha projects a wish onto reality, so it is subjunctive. That contrast is the heartbeat of the Portuguese mood system.

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English collapses this distinction with the infinitive: "I want you to come." Portuguese cannot — it needs a full subordinate clause with its own conjugated verb: quero que você venha. Whenever the two clauses have different subjects and the main verb expresses will, emotion, or doubt, expect que + subjunctive.

Adjective (relative) clauses

An adjective clause modifies a noun, just as an adjective would — it tells you which one. It is introduced by a relative pronoun, the workhorse being que (which here means "that / which / who," not "that" as a conjunction).

O livro que comprei é ótimo.

The book that I bought is great.

Conheço a moça que mora no apartamento de cima.

I know the girl who lives in the upstairs apartment.

The clause que comprei describes o livro — it narrows down which book. Relative que covers people and things alike, where English splits "who" from "which." When a preposition is involved, Portuguese keeps it in front of the relative pronoun (o tema sobre o qual falamos — "the topic we talked about"), never stranded at the end as English allows. The relative system is rich enough to deserve its own treatment — see Relative Clauses.

Relative clauses can also take the subjunctive, when the noun they modify is hypothetical or not known to exist:

Procuro um apartamento que tenha varanda.

I'm looking for an apartment that has a balcony. (any such apartment — subjunctive)

Compare Moro num apartamento que tem varanda ("I live in an apartment that has a balcony" — a specific, real one — indicative). Again: real and asserted takes the indicative; hypothetical or sought-after takes the subjunctive.

Adverbial clauses

An adverbial clause modifies the whole main clause the way an adverb would — telling when, why, if, despite what, so that, or with what result. Each meaning has its own subordinating conjunction, and the conjunction dictates the mood.

Meaning	Conjunction	Typical mood
Time	quando, depois que, assim que	indicative (past) / future subjunctive (future)
Cause	porque, já que, como	indicative
Condition	se, caso	se: indicative/future subjunctive; caso: present subjunctive
Concession	embora, ainda que, mesmo que	subjunctive
Purpose	para que, a fim de que	subjunctive
Result	de modo que, tanto que	indicative

Quando eu chegar, te ligo.

When I get there, I'll call you. (future → future subjunctive 'chegar')

Não saí porque estava chovendo.

I didn't go out because it was raining. (cause → indicative)

Embora estivesse cansado, ele continuou trabalhando.

Although he was tired, he kept working. (concession → subjunctive)

Falei devagar para que todos entendessem.

I spoke slowly so that everyone would understand. (purpose → subjunctive)

Notice the pattern. Causal and result clauses state facts, so they take the indicative. Concessive and purpose clauses point at something not asserted as fact — a concession set against expectation, a purpose not yet achieved — so they take the subjunctive. Embora is the cleanest example: it always triggers the subjunctive, with no exceptions.

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Don't memorize mood conjunction by conjunction in isolation. Memorize the logic: clauses that assert reality (cause, result, real time references) take the indicative; clauses that flag the unreal, the desired, the hypothetical, or the conceded (concession, purpose, condition with caso) take the subjunctive. The conjunction is just a signpost for which world the clause lives in.

Time clauses about the future: the future subjunctive

One feature has no English parallel and deserves its own flag. When a time or condition clause points to the future, Portuguese uses the future subjunctive — a tense English handles with the simple present.

Assim que eu terminar, eu te aviso.

As soon as I finish, I'll let you know.

Se você precisar de ajuda, é só chamar.

If you need help, just call.

English says "as soon as I finish" (present) for a future event; Portuguese marks the future-ness with terminar, precisar — the future subjunctive. This is one of the most reliable tells of a learner who has truly internalized Portuguese subordination versus one translating from English.

Common Mistakes

❌ Eu acho vai chover.

Incorrect — the conjunction 'que' is mandatory in Portuguese noun clauses.

✅ Eu acho que vai chover.

I think it's going to rain.

❌ Quero que você vem à minha festa.

Incorrect — 'querer que' with a different subject requires the subjunctive.

✅ Quero que você venha à minha festa.

I want you to come to my party.

❌ Embora ele estava cansado, continuou.

Incorrect — 'embora' always takes the subjunctive.

✅ Embora ele estivesse cansado, continuou.

Although he was tired, he kept going.

❌ Quando eu chego, te ligo. (meaning a future arrival)

Incorrect — a future time clause needs the future subjunctive, not the present indicative.

✅ Quando eu chegar, te ligo.

When I get there, I'll call you.

The throughline is mood. English speakers under-use the subjunctive because their language barely has one and leans on infinitives instead. In Portuguese, the subordinator tells you which world the clause inhabits — fact or not-yet-fact — and that decides the verb. Master the indicative/subjunctive split inside subordinate clauses and complex sentences stop being a hurdle.

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