Definition · Plain-language
Dependent clause
A dependent clause is a group of words with a subject and a predicate that cannot stand alone as a sentence because it is introduced by a subordinating conjunction or relative pronoun that makes it rely on a main clause for meaning.
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What makes a clause dependent — and the three types
A dependent clause has both a subject and a finite verb, just like an independent clause, but it cannot function as a complete sentence because of the subordinating element that opens it. The word although, because, when, who or which forces the clause to lean on an independent clause to complete the meaning. There are three types. Adverbial clauses modify the verb of the main clause and are introduced by subordinating conjunctions (because, although, since, when, while, if, unless): "Because the funding was cut, the project stalled." Adjectival or relative clauses modify a noun and are introduced by a relative pronoun (who, whom, whose, which, that): "The researcher who led the project has since retired." Noun clauses act as a subject or object and are often introduced by that: "That the results were significant surprised everyone."
Punctuation: when to use a comma
The placement of a dependent clause within a sentence determines its punctuation. When the dependent clause comes before the independent clause — the fronted position — a comma follows it: "Although the data were promising, the sample size was too small." When the dependent clause follows the main clause, no comma is normally needed: "The sample size was too small although the data were promising." This is the standard rule, but contrast conjunctions (although, whereas, even though) often attract a comma even in the trailing position. Relative clauses follow their own comma rule based on whether they are restrictive or non-restrictive, covered separately under relative clauses.
Common errors involving dependent clauses
The most frequent error is treating a dependent clause as a complete sentence — a sentence fragment. "Because the deadline was moved." looks sentence-shaped but is grammatically incomplete; it needs a main clause: "Because the deadline was moved, we rescheduled the meeting." Another error is the misuse of relative pronouns: that is used for restrictive clauses identifying which one; which is used for non-restrictive clauses adding extra information and set off by commas. Mixing these up is not merely a style issue — it changes the meaning of the sentence. Mastering dependent clauses is essential for writing well-constructed complex and compound-complex sentences.
Key facts
At a glance
- Definition: a clause with subject + predicate that cannot stand alone
- Introduced by: subordinating conjunction (because, although, when, if) or relative pronoun
- Three types: adverbial, adjectival/relative, noun
- Fronted dependent clause: always followed by a comma
- Trailing dependent clause: usually no comma (exceptions with contrast conjunctions)
- Common error: punctuating a dependent clause as a complete sentence (fragment)
Common misconceptions
What people often get wrong
Often heard: A dependent clause that begins with "because" is always a sentence fragment.
Actually: A clause beginning with because is a dependent clause — a fragment only if it stands alone. When it is joined to an independent clause, it forms a grammatical complex sentence: "Because the deadline was moved, we rescheduled the meeting."
Often heard: You should put a comma before every dependent clause.
Actually: The comma rule depends on position. A dependent clause before the main clause takes a comma after it. A dependent clause after the main clause usually takes no comma, unless it is a non-restrictive relative clause or follows a contrast conjunction such as although.
Often heard: Dependent and relative clauses are different things.
Actually: A relative clause is a type of dependent clause — specifically, an adjectival dependent clause introduced by a relative pronoun. All relative clauses are dependent clauses, but not all dependent clauses are relative clauses.
Going deeper
