The subordinating conjunctions link a dependent clause to another main clause and mark the sense relation between them. They introduce values of cause, concession, condition, purpose, time, proportion, consequence and completive. In Portuguese, the choice of the conjunction also helps define the verbal mood of the subordinate clause, especially between indicative and subjunctive. To understand the general structure of the dependence between clauses, it is worth revisiting Conjunctions and Subordinate Clauses.

Causal clauses indicate the reason or explanation for an action, as in constructions with because, since and as. They normally present a fact considered real, so they tend to appear with the indicative. The causal clause usually explains the cause of the main clause and can come before or after it, with the comma varying according to position and emphasis.

IdeiaIdea	ExemploExample
A conjunção porque introduz a causa mais comum e direta.The conjunction because introduces the cause most common and direct.	Não fui porque estava doente.I didn’t go because I was sick.
A expressão visto que apresenta a causa com tom mais formal.The expression since presents the cause with a more formal tone.	Saí cedo visto que havia pouca luz.I left early since there was little light.
A forma pois que aparece em registo mais literário ou antigo.The form as/for which appears in a more literary or old register.	Faltou pois que se sentia mal.There was a lack because he felt ill.

Concessives introduce an idea that contrasts with the main clause, without preventing the result expressed in it. Conjunctions such as although, even if and even that commonly require the subjunctive when expressing hypothesis, opposition or irrelevance of the fact to the main action. The comma is frequent because the concessive clause is usually highlighted before or after the main clause.

IdeiaIdea	ExemploExample
Embora apresenta uma concessão clássica e muito usada.Although presents a classic and widely used concession.	Saiu embora chovesse.He left although it rained.
Mesmo que exprime concessão hipotética ou eventual.Even if expresses hypothetical or eventual concession.	Irei mesmo que haja atraso.I will go even if there is a delay.
Ainda que reforça a oposição entre as duas orações.Even though reinforces the opposition between the two clauses.	Continuou ainda que estivesse cansado.He continued even though he was tired.

Conditionals present a condition for the main action to take place, as in structures with if, case and provided that. When the condition is presented as a possibility, the verb in the subordinate clause may take the subjunctive; when the condition is seen as a more certain fact, the indicative may arise in some contexts. The conditional clause can come before the main clause, which favors the comma, or after, when the link is more continuous.

IdeiaIdea	ExemploExample
Se introduz a condição mais geral e frequente.If introduces the more general and frequent condition.	Iremos se o tempo permitir.We will go if the weather allows.
Caso marca condição eventual ou incerta.Case marks an eventual or uncertain condition.	Ligue caso precise de ajuda.Call if you need help.
Desde que introduz condição de limite ou requisito.Provided that introduces a limiting condition or requirement.	Pode entrar desde que traga identificação.You may enter provided that you bring identification.

Final clauses indicate objective, intention or purpose, and appear with para que and a fim de que. These conjunctions normally require the subjunctive because the action is still desired or planned, not a completed fact. In colloquial language, the purpose can also appear with a reduced infinitive, especially when the subject is the same in both clauses.

IdeiaIdea	ExemploExample
Para que expressa objetivo direto.Para que expresses direct objective.	Estudou para que passasse.He studied so that he would pass.
A fim de que introduz finalidade mais formal.A fim de que introduces more formal purpose.	Chegou cedo a fim de que tudo começasse na hora.He arrived early so that everything would start on time.
A finalidade pode aparecer em forma reduzida no uso coloquial.The purpose can appear in reduced form in colloquial use.	Fechou a porta para não haver barulho.He closed the door to avoid noise.

Temporal clauses situate the action in time and use conjunctions such as quando, enquanto and assim que. When they indicate a future or not yet realized fact, the subjunctive is common; when they indicate a habitual or simultaneous fact, the indicative is the most natural mood. The position of the temporal clause does not alter the basic meaning, but can change the punctuation between the clauses.

IdeiaIdea	ExemploExample
Quando introduz um momento específico ou futuro.When introducing a specific or future moment.	Avise me quando chegar.Let me know when you arrive.
Enquanto marca simultaneidade.While marks simultaneity.	Estudava enquanto o irmão dormia.I studied while my brother was sleeping.
Assim que indica posterioridade imediata.As soon as indicates immediate posteriority.	Sairemos assim que acabar a chuva.We will leave as soon as the rain ends.

Proportional clauses indicate increase, decrease or correspondence between two actions or qualities, as in quanto or quanto more. They show that a change in the first clause accompanies a change in the second. The structure typically appears with the indicative, because it describes an observable correlation between the two members of the sentence.

IdeiaIdea	ExemploExample
À medida que mostra evolução paralela.As the day advances shows parallel evolution.	À medida que o dia avança, a sala enche.As the day advances, the room fills.
Quanto mais estabelece comparação crescente.The more establishes a growing comparison.	Quanto mais treina, melhor fica.The more he trains, the better he gets.
A proporção liga dois movimentos em paralelo.The proportion links two movements in parallel.	À medida que chove, o rio sobe.As it rains, the river rises.

Consecutive clauses express consequence or result, with conjunctions such as de modo que and de sorte que. They show the effect produced by an intensity, action or preceding circumstance. In general they appear after an intensifying term in the main clause, and the verb in the subordinate clause is usually in the indicative when the consequence is presented as a fact.

IdeiaIdea	ExemploExample
De modo que introduz o resultado de uma ação anterior.De modo que introduces the result of a preceding action.	Falou alto de modo que ouviram.He spoke loudly so that they heard.
De sorte que marca consequência clara e enfática.De sorte que marks a clear and emphatic consequence.	Trabalhou tanto de sorte que terminou cedo.He worked so hard that he finished early.
A consequência pode reforçar um efeito já percebido.The consequence can reinforce an effect already perceived.	Correu depressa de modo que chegou primeiro.He ran fast so that he arrived first.

Completives, also called substantive clauses, function as complements of verbs, nouns or adjectives and are frequently introduced by que and, in some cases, by se when in indirect discourse or doubt. The completive clause normally corresponds to an idea of content, desire, hope, certainty or indirect question. In many contexts, the main verb determines the mood of the subordinate clause, favoring the subjunctive when there is desire, doubt or an indirect command.

IdeiaIdea	ExemploExample
Que introduz conteúdo completivo com muita frequência.Que introduces completive content very frequently.	Espero que venhas.I hope you come.
Se aparece em perguntas indiretas e dúvida.Se appears in indirect questions and doubt.	Não sei se ele virá.I don’t know if he will come.
O verbo principal pode exigir subjuntivo por valor de desejo.The main verb may require subjunctive for wishful value.	Desejo que tudo corra bem.I wish everything goes well.

In subordinate clauses, the indicative appears when the clause presents a fact considered real, habitual or certain. The subjunctive appears when the clause expresses hypothesis, desire, possibility, purpose or concession. The choice of mood depends more on the semantic relation with the main clause than on the conjunction alone, so the same conjunction can combine with different moods depending on the context.

IdeiaIdea	ExemploExample
O indicativo apresenta fato, certeza ou constatação.The indicative presents fact, certainty or observation.	Sei que ele chegou.I know that he arrived.
O subjuntivo apresenta hipótese, desejo ou eventualidade.The subjunctive presents hypothesis, desire or eventuality.	Quero que ele chegue.I want him to arrive.
A mesma conjunção pode mudar de modo conforme o sentido.The same conjunction can change mood depending on the meaning.	Quando chega, liga.When he arrives, call.

The subordinating conjunction begins the subordinate clause and creates syntactic dependence relative to the main clause. This clause can come before or after the main one, but the comma is more common when the subordinate clause comes first, especially in concessive and temporal cases. In colloquial use, the conjunction can be omitted in certain contexts or the subordinate clause can appear reduced, particularly with an infinitive.

IdeiaIdea	ExemploExample
A conjunção normalmente abre a oração dependente.The conjunction normally opens the dependent clause.	Quando chegar, avise me.When you arrive, let me know.
A vírgula aparece com frequência quando a subordinada vem antes.The comma often appears when the subordinate clause comes first.	Embora estivesse cansado, continuou.Although he was tired, he continued.
No uso coloquial, a subordinada pode surgir reduzida.In colloquial use, the subordinate clause can appear reduced.	Saí para comprar pão.I went out to buy bread.

Subordinating conjunctions organize the link between a main clause and a dependent clause, specifying cause, concession, condition, purpose, time, proportion, consequence or content. The correct interpretation depends on the sense relationship and also on the verbal mood that the subordinate clause requires in each case. With careful use of conjunctions, punctuation and mood, the sentence gains precision and naturalness in Portuguese.