Subordinating conjunctions are used to connect the main clause and the subordinate clause, making one sentence contain the content of the other sentence. Subordinating conjunctions determine the syntactic role of the subordinate clause within the full sentence. Subordinating conjunctions commonly introduce semantic relations such as cause, condition, time, result, and concession. The common Chinese structure is main clause + subordinating conjunction + subordinate clause or subordinate conjunction + subordinate clause + main clause.

Because... therefore... expresses cause and effect, commonly used in dialogue or written explanations of reasons. Because introduces the cause clause, therefore introduces the result; they can be used together or separately. In spoken language, one part is often omitted, but the logical relationship remains unchanged.

So expresses the result, usually following the preceding cause, regardless of whether the preceding cause is explicitly marked with because. Then expresses the sequential result, often used to describe the development of events, with a stronger sense of action progression than so. Result emphasizes an unexpected or concluding outcome, often appearing at the end of a narrative, with a concluding tone.

If ... then ... expresses a general condition, and the corresponding result. The most common conditional structure. Only if ... then ... expresses a sufficient condition, with a tone more definite. Unless ... expresses a negative condition, often paired with then or otherwise, highlighting the exception.

When ... or when ... indicates a time clause, showing a moment or duration. After ... indicates something happening afterward, often used with then to express the immediate following action. Before ... indicates something occurring before, with the main clause typically containing prior preparation or arrangements. As soon as ... indicates two actions closely linked, often used to describe habits or automatic responses.

In order to introduces purpose, often placed at the beginning of a sentence or before the verb, indicating the goal of the action. So that introduces purpose; the style is more formal, common in writing or formal occasions. To used as a connective expresses purpose; common in the pattern ..., to ..., with a colloquial tone.

Although ... but ... expresses concession, contrasting expectation and reality, common in spoken and written language. Even though ... also expresses concession, slightly formal, can be paired with but or still. Even if ... expresses hypothetical concession, emphasizing that even if a certain situation occurs, the result does not change, often paired with also.

Not only ... but also ... expresses progression, linking two positive contents, emphasizing the second. While ... and ... expresses two actions happening at the same time. Not ... is a choice or possibility, listing two cases. If not ... then ... can be combined with a condition to express a more specific contrasting choice.

When a Chinese subordinating conjunction is fronted, the usual order is the subordinating conjunction + subordinate clause + main clause, suitable for highlighting conditions, reasons, or time. In medial position, the common form is main clause + subordinating conjunction + subordinate clause, suitable for adding information. Long sentences tend to place the subordinate clause first to help the listener or reader grasp the context. When using conjunctions, ensure that both the main clause and the subordinate clause express complete meaning; avoid fragments.

Complex sentences can nest or chain multiple subordinate conjunctions, but each clause should have a clear semantic relation. A common approach is to combine time, condition, or reason clauses with a result clause. Choosing conjunctions wisely helps prevent ambiguity and keeps the sentence logic clear. When sentence length increases, organize information in the order time/condition/reason → result/decision.