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📝 English and Language Usage · Conventions of Standard English · Lesson 6 of 6 · 6 min

Sentence types: simple, compound, complex and compound-complex

🏗️ Name a sentence's type by counting its clauses. Once you can spot independent and dependent clauses, these questions take seconds.

💡 Key idea

Count clauses: 1 independent = simple; 2+ independent = compound; 1 independent + dependent = complex; 2+ independent + dependent = compound-complex.

🧠 The idea

Classify by clauses, not by length. A SIMPLE sentence has one independent clause; it may have a compound subject or verb and many phrases: "Nurses and aides lifted and turned the patient after lunch." A COMPOUND sentence has two or more independent clauses joined by a coordinating conjunction (for, and, nor, but, or, yet, so) or a semicolon: "The alarm rang, and we left." A COMPLEX sentence has one independent clause and at least one DEPENDENT CLAUSE, which starts with a subordinating word such as because, although, when, if, since, while, after or a relative pronoun (who, which, that): "When the alarm rang, we left." A COMPOUND-COMPLEX sentence has at least two independent clauses and at least one dependent clause: "When the alarm rang, we left, but the guard stayed." Tip: a phrase ("after lunch," "running fast") has no subject-verb pair, so it never changes the type.

✏️ Worked example

"Although the clinic was busy, Dr. Hall saw every patient, and she still left on time." Step 1: mark subject-verb pairs: clinic was, Dr. Hall saw, she left. Step 2: "Although the clinic was busy" starts with a subordinator, so it is dependent. Step 3: "Dr. Hall saw every patient" and "she still left on time" can each stand alone: two independent clauses joined by ", and." Step 4: two independent + one dependent = compound-complex.

📌 Takeaways

  • Phrases do not count; only subject-verb clauses decide the type.
  • A compound subject or verb still makes a simple sentence.
  • Because, although, when, if and who start dependent clauses.

📖 Terms in this lesson

Complex sentence: A sentence with one independent clause and at least one dependent clause; for example, "When the alarm rang, the nurse checked the monitor."

✅ Check yourself

Question 1 of 3

What type of sentence is this? "The students and their teacher walked to the museum and toured the exhibits."

  1. Simple
  2. Compound-complex
  3. Compound
  4. Complex
Show the answer and rationale

Answer: A

There is one independent clause with a compound subject (students and teacher) and a compound verb (walked and toured), so it is simple. It has no second independent clause and no dependent clause.

Question 2 of 3

What type of sentence is this? "I will call you after the results arrive."

  1. Simple
  2. Complex
  3. Compound-complex
  4. Compound
Show the answer and rationale

Answer: B

"I will call you" is independent, and "after the results arrive" is a dependent clause with its own subject and verb, so the sentence is complex. It is not compound because there is only one independent clause.

Question 3 of 3

Which sentence is compound?

  1. Because it snowed, school closed.
  2. The bus arrived late, so we missed the first class.
  3. The bus that arrived late was crowded.
  4. After the long ride, we rested.
Show the answer and rationale

Answer: B

Two independent clauses ("The bus arrived late" and "we missed the first class") are joined by ", so," making it compound. The "because" and "that" sentences are complex, and "After the long ride" is a phrase, so that sentence is simple.

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