Relative Clauses - Identifying vs. Non-identifying
If the information in a relative clause is necessary, you do not put commas around it. This is called an “identifying relative clause” (because the information is necessary to “identify” the subject).
However, if the information in the relative clause is not necessary -- if it is just extra information about the subject -- then you put commas around the relative clause. This is called a “non-identifying relative clause” (because the information is not necessary to identify the subject).
*With non-identifying relative clauses, you cannot use “that” – you must use “which” instead
That dog, which only has three legs, is my dog.
(“which only has three legs” is not necessary to identify this dog)
You might say this sentence if you are looking at one specific dog.
The dog that/which only has three legs is my dog.
(“which only has three legs” is necessary to identify this dog)
You might say this sentence if you are looking at several dogs, and you use the clause “which only has three legs” to identify one specific dog.
Billy, who drives a red pickup, was caught speeding last night.
(“who drives a red pickup” is not necessary to identify Billy – it is extra information, so you put commas around it )
Read these sentences and find the relative clauses. If the information is not necessary (if it is just extra information about the subject), put commas around the relative clause.
1. California which has the nation’s largest economy is on the west coast.
2. James who moved here just two weeks ago won the spelling bee.
3. The movie which I was talking about will come to the local movie theater next week.
4. Barack Obama whose father was from Kenya became President of the USA.
5. The man that I saw had dark hair.
6. England where Dave grew up has some of the best universities in the world.
7. The neighborhood where I grew up was very safe and quiet.
8. Santa Claus who wears a red suit and has a long white beard is loved by children everywhere.
9. This book which was written over one hundred years ago has some very interesting facts.
10. The amusement park where people of all ages come to relax and have fun will close next year.
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