Subordinating Conjunctions, Complex Sentences, and Punctuation Rules

Subordinating Conjunctions and Complex Sentence Mechanics

In academic English, writers frequently connect ideas that are not equal in importance. Subordination is the grammatical process of linking two clauses so that one clause is dependent on (subordinate to) the other. The clause containing the subordinating conjunction becomes a dependent (subordinate) clause, functioning as an adverb that modifies the main action by providing context regarding cause, condition, contrast, or time.

A sentence containing one independent main clause and at least one dependent clause is classified as a complex sentence. Unlike coordinating conjunctions, which join equal independent clauses, subordinating conjunctions establish a clear structural hierarchy: the main clause conveys the primary assertion, while the subordinate clause provides supporting conditions or reasons.

Logical Categories of Subordinating Conjunctions

To select the correct subordinating conjunction on the ACCUPLACER ESL exam, candidates must understand the precise logical relationship being established between clauses:

Punctuation Rules for Complex Sentences

Punctuation in complex sentences depends entirely on the position of the dependent clause relative to the independent main clause.

Rule 1: Introductory Subordinate Clause → Comma Required

When a dependent clause appears at the beginning of a sentence (preceding the main clause), it acts as an introductory element. A comma must be placed at the end of the dependent clause, immediately before the independent clause begins.

• Formula: [Subordinating Conjunction] + [Subject 1] + [Verb 1] + , + [Subject 2] + [Verb 2]
• Correct Example: Although the survey sample was small, the findings provided valuable qualitative insights.
• Analysis: The introductory clause Although the survey sample was small cannot stand alone. The comma signals the transition to the main independent clause the findings provided valuable qualitative insights.

Rule 2: Terminal Subordinate Clause → No Comma (General Rule)

When the independent main clause comes first and the dependent clause follows it, no comma is generally required before the subordinating conjunction. The conjunction itself serves as the boundary marker between the clauses.

• Formula: [Subject 1] + [Verb 1] + [Subordinating Conjunction] + [Subject 2] + [Verb 2]
• Correct Example: The findings provided valuable qualitative insights because the research team conducted thorough interviews.
• Analysis: Because the dependent clause because the research team conducted thorough interviews appears at the end of the sentence, no comma should separate it from the main clause.

Rule 3: The Concession / Strong Contrast Exception

An important exception to Rule 2 occurs with subordinate clauses introducing strong contrast or concession (using although, even though, whereas, or while). When these contrast clauses appear at the end, a comma can clarify the unexpected contrast or prevent misreading.

• Correct Example: The team completed the laboratory report on schedule*, although several key data points were still missing.*
• Analysis: The comma before although clarifies that the second clause represents an unexpected concession rather than a direct restriction.

Common Subordination Errors

The ACCUPLACER ESL Language Use test intentionally includes common non-native writing errors as distractor options. Mastering these specific pitfalls will prevent costly mistakes:

1. The Double Conjunction Error (Redundancy Trap)

In many languages (such as Spanish, Chinese, or Arabic), it is natural to pair a subordinating conjunction with a coordinating conjunction or conjunctive adverb in the same sentence. In standard English, however, using two conjunctions to connect two clauses is ungrammatical because it leaves both clauses dependent or creates a structural conflict.

• Incorrect (Double Conjunction): Although the deadline was extended, but the student still needed assistance.
• Incorrect (Double Conjunction): Because the weather was severe, so the university canceled classes.
• Correct Option A (Subordination): Although the deadline was extended, the student still needed assistance.
• Correct Option B (Coordination): The deadline was extended, but the student still needed assistance.
• Rule for these patterns: Do not use two connectors to express the same clause relationship. Choose although or but, and choose because or resultative so.

2. Sentence Fragment Trap

A dependent clause beginning with a subordinating conjunction cannot function as a standalone sentence, even if it contains a subject and a verb. Separating a subordinate clause from its main clause with a period creates a sentence fragment.

• Incorrect Fragment: The committee approved the budget proposal. Because the projected revenues were high.
• Correct Complex Sentence: The committee approved the budget proposal because the projected revenues were high.

3. Misinterpreting Unless (Negative Conditional Trap)

The subordinating conjunction unless means if...not. Because unless already means if ... not, adding a negative often reverses the intended condition. Such a construction is not automatically ungrammatical; evaluate its literal meaning.

• Wrong for the intended condition: Unless you do not register by Friday, you cannot attend the conference.
• Correct Structure: Unless you register by Friday, you cannot attend the conference. (Meaning: If you do not register by Friday...)

4. Distinguishing Since (Time vs. Cause) and While (Time vs. Contrast)

English language learners must recognize that certain subordinating conjunctions carry multiple meanings:

• Since: Indicates time from a past point (I have lived here since 2020) OR expresses cause (Since the library is closed, we must study at home).
• While: Indicates simultaneous time (She read while he cooked) OR expresses contrast (While the first experiment failed, the second succeeded).