Constructing Complex Sentences

On grammar and editing test items, complex sentences are tested less for whether you can define them and more for whether you can punctuate them correctly under pressure. You are expected to already recognize an independent clause and a dependent clause on sight; the real skill being assessed is applying the comma rule that governs their order, and catching the two most common distractor errors: the fragment disguised as a sentence, and the comma splice disguised as a correctly joined one.

A complex sentence joins one independent clause with at least one dependent clause introduced by a subordinating conjunction. The punctuation required depends entirely on which clause comes first, so the first move on any test item is to locate the subordinating conjunction and determine whether its clause opens or closes the sentence.

Pattern 1: Dependent Clause First

When the dependent clause precedes the independent clause, it is set off with a comma. For example: "Although it was raining, we finished the hike." The comma signals the reader that the introductory clause has ended and the main idea is about to begin.

Pattern 2: Independent Clause First

When the dependent clause follows the independent clause, no comma is generally used, because the subordinating conjunction already marks the boundary clearly: "We finished the hike although it was raining."

One nuance worth knowing for test items: contrastive conjunctions such as "although," "though," "even though," and "whereas" sometimes keep a comma even in the second position, because the clause they introduce adds a contrast rather than an essential condition. Compare "We finished the hike, although the trail was muddy" (contrast, comma optional but acceptable) with "We will reschedule if it rains" (condition, no comma).

Test items often disguise the relationship a conjunction signals, so it helps to sort conjunctions by the logical connection they create rather than memorizing them as an undifferentiated list.

Time

When, while, before, after, until, as soon as. Example: "The committee adjourned before the vote was finalized."

Cause and Effect

Because, since, so that, as. Example: "The proposal was revised because the data contradicted the original claim."

Condition

If, unless, provided that, as long as. Example: "The policy takes effect unless the board objects in writing."

Contrast

Although, though, even though, whereas. Example: "The results were inconclusive, whereas the pilot study had shown a clear trend."

Fragments Disguised as Sentences

A dependent clause punctuated with a period as though it were complete is a classic distractor: "Because the evidence was inconclusive." This has a subject and a verb, but the subordinating conjunction leaves the thought unfinished; it must be attached to an independent clause to form a complete sentence.

Comma Splices Mistaken for Subordination

Joining two independent clauses with only a comma, with no subordinating conjunction, is a comma splice, not a complex sentence: "The evidence was inconclusive, the committee delayed its ruling." Correcting it requires either a subordinating conjunction ("Because the evidence was inconclusive, the committee delayed its ruling") or a different form of punctuation entirely.

Consider the flawed sentence: "Since the budget was approved the project began immediately." The subordinating conjunction "since" opens the sentence, so the dependent clause "Since the budget was approved" requires a comma before the independent clause begins. The corrected sentence reads: "Since the budget was approved, the project began immediately." Reversing the clause order removes the need for the comma: "The project began immediately since the budget was approved."

Related lessons

• Complex sentences