Source: Identifying Clauses Practice 1 Answer Key, English Composition II (Purdue University)
Difficulty: Beginner | Prerequisites: Basic understanding of subjects and verbs in English sentences.
Clauses are the building blocks of every sentence you write. Before you can fix run-ons, splice commas correctly, or combine ideas with subordination, you need to tell the difference between a clause that can stand alone (independent) and one that cannot (dependent). This skill underpins almost every grammar and composition topic you will meet in ENG 101 and beyond. If you can identify subjects and verbs, you are ready to start here.
A clause contains a subject and a verb. An independent clause expresses a complete thought and can be a sentence on its own. A dependent clause starts with a subordinating word (like "although" or "when") and cannot stand alone. Some word groups that look like clauses are just phrases, with no subject-verb pair at all.
Clause
A group of words that contains both a subject and a verb. Think of it as the minimum unit that can express an action or state with someone doing it.
Independent clause (main clause)
A clause that expresses a complete thought and can stand on its own as a sentence. In simple terms, if you put a full stop after it and it still makes sense, it is independent.
Dependent clause (subordinate clause)
A clause that contains a subject and a verb but cannot stand alone as a sentence because it begins with a subordinating conjunction or relative pronoun. Think of it as a clause that leans on the rest of the sentence for its meaning.
Subordinating conjunction
A word that introduces a dependent clause and links it to an independent clause. Common examples: although, because, since, when, whenever, while, before, after, if, unless, until.
Relative pronoun
A pronoun that introduces a dependent (relative) clause and refers back to a noun in the main clause. Common examples: who, whom, whose, which, that.
Phrase (not a clause)
A group of related words that does NOT contain both a subject and a verb working together. In simple terms, a phrase is missing one or both of those pieces, so it can never be a clause. A prepositional phrase like "after the flood" or a participial phrase like "before completing the assignment" are common lookalikes.
Find the verb (the action or state of being).
Find the subject (who or what performs the action).
If both are present, you have a clause. If either is missing, it is a phrase.
An independent clause has a subject, a verb, and a complete thought. It does not begin with a subordinating conjunction or relative pronoun.
"John saw a raccoon eating potato chips" (subject: John, verb: saw, complete thought)
"Students enrolled in bachelor's and associate's degree programs must pass the Regents' Test as a graduation requirement" (subject: Students, verb: must pass, complete thought)
Both of these can stand as full sentences with nothing added or removed.
A dependent clause has a subject and a verb but opens with a subordinating word that makes it incomplete. Remove the subordinating word and the clause becomes independent.
"Although it was raining" (subordinating conjunction: although, subject: it, verb: was raining, but the thought is incomplete)
"whenever she gets a poor grade in math" (subordinating conjunction: whenever)
"who fail to show up for the Regents' test" (relative pronoun: who)
"When you finish your homework" (subordinating conjunction: when)
"After Juan completed the assignment" (subordinating conjunction: after)
"since she had to drive to Atlanta for a meeting" (subordinating conjunction: since)
Each of these leaves the reader asking, "So what happened?" That is the hallmark of a dependent clause.
Some word groups begin with the same words that start dependent clauses (after, before, while) but contain no subject-verb pair. These are phrases, not clauses.
"After the flood" is a prepositional phrase. There is no subject doing anything and no conjugated verb. Compare with "After Juan completed the assignment," which has a subject (Juan) and a verb (completed).
"Before completing the assignment" is a participial/prepositional phrase. "Completing" is a gerund here, not a finite verb with its own subject. Compare with "Before he completed the assignment," which would be a dependent clause.
The test: can you point to a subject AND a finite verb inside the word group? No? Then it is a phrase.
Students often think that any word group starting with "after," "before," or "while" is automatically a dependent clause. It is only a clause if it contains its own subject and finite verb. "After the flood" has no verb, so it is a prepositional phrase.
Students often assume that a long word group must be a clause. Length has nothing to do with it. "Before completing the incredibly difficult and time-consuming assignment" is still just a phrase, no matter how many words it contains.
Students sometimes label a dependent clause as independent because it contains a subject and a verb. The presence of a subordinating word (although, because, when, who, etc.) is what makes it dependent. If you strip the subordinating word away and the clause makes sense on its own, that confirms it was the subordinating word creating the dependency.
Students occasionally forget that relative pronouns (who, which, that) can introduce dependent clauses, not only subordinating conjunctions. "Who fail to show up for the Regents' test" is a dependent clause introduced by a relative pronoun.
⚠️ Exams frequently underline a word group and ask you to classify it as independent clause, dependent clause, or not a clause. The "not a clause" option is the trap: prepositional and participial phrases are designed to look like dependent clauses.
⚠️ You will need this skill for comma rules. A dependent clause at the start of a sentence takes a comma after it ("When you finish your homework, please take the dog for a walk"). Misidentifying the clause type leads to comma errors.
⚠️ Sentence combining questions depend on knowing which clause is independent and which is subordinate. If you cannot tell them apart, you cannot fix fragments, run-ons, or comma splices.
⚠️ The distinction between "after + noun" (phrase) and "after + subject + verb" (clause) is a commonly tested pattern. Expect at least one question built around it.
Answer true or false. Check your answers against the Key Terms and Core Content sections above.
True or false: Every group of words that begins with "because" is a dependent clause.
True or false: An independent clause can stand alone as a complete sentence.
True or false: "After the storm" is a dependent clause because it starts with "after."
True or false: A dependent clause always contains a subject and a verb.
True or false: Removing the subordinating conjunction from a dependent clause turns it into an independent clause.
Answers: 1. True ("because" always introduces a dependent clause, provided a subject and verb follow). 2. True. 3. False (it is a prepositional phrase with no subject-verb pair). 4. True. 5. True.
Q: Identify the underlined portion: "Because the library was closed, we studied at home." (Underlined: "Because the library was closed")
A: Dependent clause. It has a subject (library) and a verb (was closed), and it begins with the subordinating conjunction "because," so it cannot stand alone.
Q: Identify the underlined portion: "The manager reviewed the budget and approved the plan." (Underlined: "The manager reviewed the budget")
A: Independent clause. It has a subject (manager), a verb (reviewed), and expresses a complete thought.
Q: Identify the underlined portion: "During the meeting, everyone agreed on the deadline." (Underlined: "During the meeting")
A: Not a clause. "During the meeting" is a prepositional phrase. There is no subject performing an action and no finite verb.
Q: What is the difference between "after the game" and "after the game ended"?
A: "After the game" is a prepositional phrase (no subject-verb pair). "After the game ended" is a dependent clause: it has a subject (game), a verb (ended), and the subordinating conjunction "after" makes it dependent.
Q: Can a dependent clause become an independent clause? How?
A: Yes. Remove the subordinating conjunction or relative pronoun. For example, "when she arrived" becomes "she arrived," which is a complete sentence on its own.
This connects to sentence structure and sentence types (simple, compound, complex, compound-complex) because each type is defined by its combination of independent and dependent clauses. You cannot classify sentence types without first identifying the clauses.
This also connects to punctuation rules for commas, semicolons, and colons. Comma placement after introductory dependent clauses, comma use in compound sentences, and the avoidance of comma splices all depend on recognising clause boundaries.
Finally, understanding dependent clauses ties into the study of sentence fragments. A dependent clause punctuated as a sentence is one of the most common fragment errors in student writing.
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