What a clause needs
A clause is a group of words with a subject and a finite verb. The finite verb shows tense. "She waits" is a clause. "Waiting for the bus" is not a clause, because it has no subject and no finite verb. It is a phrase.
| Group of words | Subject? | Finite verb? | Clause? |
|---|---|---|---|
| the train leaves | the train | leaves | Yes |
| after the film | no | no | No, a phrase |
| because she was tired | she | was | Yes |
| to catch the early bus | no | no | No, a phrase |
The main clause
A main clause can stand alone as a complete sentence. It carries the main statement. Every complete sentence has at least one main clause.
- Main clause: The library closes at six.
- Main clause: My brother cooked dinner.
- Main clause: We missed the last train.
One sentence can hold two main clauses. A coordinating conjunction such as and, but, or or so joins them. The result is a compound sentence.
The library closes at six, so we left at five.
Each half of that sentence can stand alone. "The library closes at six" is a sentence. "We left at five" is a sentence. The conjunction joins two equal parts.
The subordinate clause
A subordinate clause has a subject and a finite verb, but it cannot stand alone. It starts with a subordinating word and it depends on a main clause. It adds information: a reason, a time, a condition, a person or a thing.
- Because the library closes at six, we left at five.
- We left at five because the library closes at six.
"Because the library closes at six" is not a sentence on its own. A reader waits for the rest. That waiting feeling is the test for a subordinate clause.
Three jobs of a subordinate clause
| Job | Common words | Example |
|---|---|---|
| Adverbial: gives time, reason, condition or contrast | because, although, when, while, if, unless, before, after, so that | We stayed inside because it was raining. |
| Relative: describes a noun | who, which, that, whose, where | The teacher who called me was very patient. |
| Noun: acts as the object or subject of a verb | that, whether, what, why, how | I think that the plan will work. |
Word order and commas
The position of the subordinate clause decides the comma.
Although the room was cold, nobody closed the window.
Subordinate clause first: use a comma between the two clauses.
Nobody closed the window although the room was cold.
Main clause first: no comma is needed before a short subordinate clause.
Although the room was cold, but nobody closed the window.
Use one connector, not two. "Although" already signals the contrast.
Common mistakes
| Mistake | What happened | Fix |
|---|---|---|
| When the bell rang. | Fragment: a subordinate clause with no main clause. | The students left when the bell rang. |
| I was late, the bus broke down. | Comma splice: two main clauses joined by a comma only. | I was late because the bus broke down. |
| She said that she was tired, that was clear. | Two statements run together. | She said that she was tired. That was clear. |
| The book who I bought. | Wrong relative pronoun for a thing. | The book that I bought. |
Choosing the right connector
Because gives a reason. Although gives a contrast and does not take but. So that gives a purpose. Unless means "if not", so do not add another negative.
That can introduce a noun clause or a relative clause. The relative clauses lesson shows when to use who, which or that. Which only describes a thing. In careful writing, which after a comma comments on the whole previous clause, while that limits the noun before it.
- Defining: The phone that I bought last year stopped working.
- Commenting: The phone stopped working, which was annoying.
Try the quiz
Answer the questions in writing first. Then open the answer key.
- Underline the main clause: When the film ended, everyone clapped.
- Add a main clause: Because the road was closed ...
- Join with although: The weather was bad. We enjoyed the trip.
- Is this a sentence? While I was waiting for the bus.
- Choose that or which: The coat ___ I bought is too small.
- Find the mistake: Although she was tired, but she finished the report.
Show all answers
- everyone clapped. "When the film ended" is the subordinate clause.
- Example: Because the road was closed, we took the train. The new part must be able to stand alone.
- Although the weather was bad, we enjoyed the trip. No "but".
- No. It is a subordinate clause and it needs a main clause.
- that. It limits the noun "coat" and there is no comma.
- "Although" and "but" both mark the contrast. Remove one of them.