Clauses are the building blocks of sentences. Independent clauses stand alone as complete thoughts, while dependent clauses need to attach to an independent clause to make sense. Getting comfortable with both types helps you write sentences that are clear, varied, and grammatically correct.
This section covers the two clause types, the conjunctions that connect them, and the sentence structures you can build by combining them.
Clauses
Types of Clauses and Their Functions
A clause is a group of words that contains both a subject and a predicate (verb). The key question is whether that clause can stand on its own.
An independent clause expresses a complete thought and works as a sentence by itself. It contains a subject and a predicate, and it doesn't need anything else to make grammatical sense.
The sun shines brightly. → Complete thought. This is an independent clause.
A dependent clause (also called a subordinate clause) has a subject and a verb, but it does not express a complete thought. It typically begins with a subordinating conjunction or a relative pronoun, and it must attach to an independent clause.
When the sun shines → Has a subject and verb, but feels incomplete. You're left asking, "What happens when the sun shines?"
Dependent clauses are categorized by the role they play in a sentence:
- Noun clauses act as subjects, objects, or complements → What he said surprised me.
- Adjective clauses modify nouns or pronouns → The book that I read was fascinating.
- Adverb clauses modify verbs, adjectives, or other adverbs → She smiled when she saw him.
One point that trips people up: "dependent clause" and "subordinate clause" mean the same thing. Likewise, "main clause" is just another name for the independent clause in a complex sentence.
Identifying and Using Clauses
To figure out whether a clause is independent or dependent, try this quick test:
- Isolate the clause from the rest of the sentence.
- Read it on its own. Does it express a complete thought?
- If yes, it's independent. If it feels unfinished or leaves you hanging, it's dependent.
Dependent clauses often start with signal words that give them away:
- Subordinating conjunctions: although, because, while, if, when, since, before, after, until
- Relative pronouns: who, whom, whose, which, that
To find the main clause in a complex sentence, remove all the dependent clauses. Whatever remains is your independent clause.
Although it was late, she finished her homework. → Remove "Although it was late" and you're left with she finished her homework, the independent clause.
Conjunctions
Coordinating Conjunctions and Their Uses
Coordinating conjunctions connect words, phrases, or clauses of equal grammatical rank. You can remember all seven with the acronym FANBOYS:
| Conjunction | Function | Example |
|---|---|---|
| For | gives a reason | I was tired, for I had worked all night. |
| And | adds information | She sang and danced. |
| Nor | connects two negatives | Neither the car nor the bike was available. |
| But | introduces contrast | He tried hard but failed. |
| Or | presents alternatives | Would you like coffee or tea? |
| Yet | shows unexpected contrast | He studied hard, yet he failed the exam. |
| So | indicates a result | It was raining, so we stayed indoors. |
When a coordinating conjunction joins two independent clauses, place a comma before the conjunction:
I like coffee*,** and I enjoy tea.*
When it joins just two words or phrases (not full clauses), skip the comma: I like coffee and tea.
Subordinating Conjunctions and Complex Sentences
Subordinating conjunctions introduce dependent clauses and connect them to independent clauses. They signal the relationship between the two clauses:
- Time: after, before, when, while, until, as soon as
- Cause/effect: because, since, as
- Condition: if, unless, provided that
- Contrast: although, though, even though
Placement matters for punctuation. When the dependent clause comes first, use a comma after it. When the independent clause comes first, you typically don't need a comma.
Because it was raining, we stayed home. (comma after the dependent clause) We stayed home because it was raining. (no comma needed)
Sentence Types
Compound Sentences: Structure and Usage
A compound sentence joins two or more independent clauses. There are three main ways to do this:
- Coordinating conjunction with a comma: I love reading, and I enjoy writing.
- Semicolon alone (when the clauses are closely related): I love reading; I enjoy writing.
- Semicolon with a conjunctive adverb: I love reading; however, I enjoy writing more.
The key rule: each clause in a compound sentence must be able to stand alone. If one side of the conjunction isn't a complete thought, you don't actually have a compound sentence.
Complex Sentences: Components and Formation
A complex sentence contains exactly one independent clause and at least one dependent clause. The dependent clause can be introduced by a subordinating conjunction or a relative pronoun.
When it rains, the plants grow. → subordinating conjunction "when" The book that I read was interesting. → relative pronoun "that"
The order of clauses is flexible:
- Dependent clause first: While I was sleeping, the phone rang. (comma required)
- Independent clause first: The phone rang while I was sleeping. (no comma needed)
Complex sentences let you show relationships between ideas, such as cause and effect, timing, or conditions, that simple and compound sentences can't express as precisely. Mixing compound and complex sentences into your writing keeps it from feeling flat or repetitive.