- Adjective clauses always begin with who, which, or that
- An adjective describes a noun or a pronoun
- A clause is a collection of words with a noun and a verb
Therefore, an adjective clause is a group of words that has a verb and describes a noun or a pronoun and begins with who, that, or which.
- any adjective clause beginning with “which” is always nonessential and has commas around it
- any adjective clause beginning with “that” is always essential and has no commas around it
Which – nonessential
- The car, which needs to be washed, needs an oil change before you drive it to Houston.
- The dog, which is very friendly, needs to be neutered tomorrow morning.
- The airplane, which has a shabby paint job, has been repaired and is ready to fly.
If you take out the adjective clauses, your sentences still have the same basic information:
- The car needs an oil change before you drive it to Houston. (doesn’t matter that it needs to be washed)
- The dog needs to be neutered tomorrow morning. (doesn’t matter that it’s friendly)
- The airplane has been repaired and is ready to fly. (doesn’t matter what kind of paint job it has)
Who – can be essential or nonessential
That woman, who is sitting alone, has just bought a Maserati. (nonessential – not important that she is alone)
That woman who is sitting alone is my sister. (essential – the clause identifies which woman you are talking about)
That – essential
- The car that you plan to take to Houston needs an oil change first.
- The dog that needs to be neutered is in the brown dog carrier.
- The airplane that needs repairs has been returned to the hangar.
You can’t take out the adjective clause, or your sentence will be missing some important information. You will still have a complete sentence, but it lacks a lot of vital information. Which car? Which dog? Which airplane?
ESSENTIAL – NO COMMAS
NONESSENTIAL – COMMAS
COMMAS – THE CLAUSE IS UNNECESSARY TO THE SENTENCE AND CAN BE REMOVED
These are phrases, often one or two words, that rename the noun or pronoun, and can be removed with no problem.
That makes them nonessential and have commas before AND AFTER.
- Your mother, a nurse, is planning to go to Europe with us.
- My dog, a greyhound, is going to the vet next week.
REMEMBER THE COMMA AFTER THE APPOSITIVE AS WELL AS THE ONE BEFORE THE APPOSITIVE. BOTH COMMAS ARE NECESSARY.