Relative clauses: non-defining relative clauses
Look at these examples to see how non-defining relative clauses are used.
Jack, who's retired now, spends a lot of time with his grandchildren.
We want to see the new Tom Carter film, which was released on Friday.
My sister, whose dog I'm looking after, is visiting a friend in Australia.
Try this exercise to test your grammar.
Read the explanation to learn more.
Grammar explanation
Relative clauses give us information about the person or thing mentioned.
Non-defining relative clauses give us extra information about someone or something. It isn't essential for understanding who or what we are talking about.
My grandfather, who's 87, goes swimming every day.
The house, which was built in 1883, has just been opened to the public.
The award was given to Sara, whose short story impressed the judges.
We always use a relative pronoun or adverb to start a non-defining relative clause: who, which, whose, when or where (but not that). We also use commas to separate the clause from the rest of the sentence.
who, which and whose
We can use who to talk about people, which to talk about things and whose to refer to the person or thing that something belongs to.
Yesterday I met my new boss, who was very nice.
The house, which is very big, is also very cold!
My next-door neighbour, whose children go to school with ours, has just bought a new car.
After the port there is a row of fishermen's houses, whose lights can be seen from across the bay.
Places and times
We can use which with a preposition to talk about places and times. In these cases it's more common to use where or when instead of which and the preposition.
City Park, which we used to go to, has been closed down.
City Park, where we used to go, has been closed down.
December, which Christmas is celebrated in, is a summer month for the southern hemisphere.
December, when Christmas is celebrated, is a summer month for the southern hemisphere.
However, when we use which without a preposition, we can't use where or when.
Centre Park, which we love, is always really busy on Saturdays.
February, which is my favourite month, lasts 29 days this year.
Do this exercise to test your grammar again.
Hello~
Can “as” be used to start a relative clause, as in “As she mentioned before, teamwork is crucial for our success.”?
If the above sentence is a relative clause, does “as” function as the object of the clause? It seems like “as” is the object of “mention”.
If “as” can serve as the subject or object in a relative clause, then why there is an “it”, serving as the object in the clause, in “Without the breakthroughs of these pioneers in science and technology, whether lucky or planned, the world as we know it today would be a completely different place.”?
Thx for your time.
Hello Radioheady,
That is not a relative clause. 'As' is a conjunction here used to join and show the relationship between clauses. Specifically, 'as' is a subordinating conjunction with a similar meaning to 'because'.
Peter
The LearnEnglish Team
Thank you for your clarification.
In the sense that as is a subordinating conjunction, is "As she mentioned before" an adverbial clause? It seems "mention" is a transitive verb. Then what is the object of "mentioned" in the clause?
What if I put the clause in passive voice, and then which one is correct?: 1. As was mentioned before, teamwork is crucial for our success. 2. As mentioned before, teamwork is crucial for our success.
In other words, why do we usually say "as expected" rather than "as is expected"? Then, why do we usually say "as is often the case" rather than "as often the case"? They all use "as" as a subordinating conjunction, and when there should be an "is"?
In terms of the sentence "Without the breakthroughs of these pioneers in science and technology, whether lucky or planned, the world as we know it today would be a completely different place," is "as we know it today" a relative clause? And according to what I have leant browsing the Internet, "as" is called a "relativizer", which I find quite confusing. I was taught that we use "as" in a relative clause when there is "the same" or "such" before the clause. But there isn't "the same" or "such" in the sentence we're discussing. Is it still a relative clause? why couldn't we leave out "it", like "Without the breakthroughs of these pioneers in science and technology, whether lucky or planned, the world as we know today would be a completely different place"? In other words, can I see "as" as the object of "know" in the clause where "it" is removed?
Thank you so much for your time. As a keen English learner, I may sound a bit pedantic in some grammar details when things don't align with what my teacher used to teach me (all of the English teachers here have been thinking that "as she mentioned" is a non-defining relative clauses). But the parsing of "as" has been a pain in my neck for years, and your clarification would mean a great deal to me.
Hello again Radioheady,
Yes, it is an adverbial clause.
As you say, mention is a transitive verb. So is 'say' and yet in the sentence before this one it is used intransitively (As you say...). In fact, you can use many transitive verbs in this construction without an object: As you prefer/like/want/request etc. We could explain this by suggesting an implied object but I think it's simply a quirk of the construction. It certainly wouldn't be the first such case in English!
Both forms are fine here.
You can include the 'is' or omit it, just as in the example above with 'was'. You can also say 'as often the case...'.
You can read about relativisers here:
https://en.wikipedia.org/wiki/Relativizer
As you can see, 'as' is not included.
If you omit 'as' then you change the meaning of the sentence. As we know... means 'according to our existing knowledge' whereas 'as we know it' means 'the world with which we are familiar'.
I understand. However, please remember that we are a small team here with limited time. It's difficult for us to respond in such detail so multiple questions like this and it's also of limited use to other learners. Really, this is a topic for discussion on a linguistics or language analysis forum rather than a language-learning site. A good place for this kind of discussion is StachExchange:
https://english.stackexchange.com/
Peter
The LearnEnglish Team
Thx a lot! Your help has made my day.
James who is a football player is my brother
James who is my brother is a football player
Are both of these are correct ?
Do we have to use commas, or they are optional in this case?
Hello Khaled.,
These are both examples of non-defining relative clauses giving extra but not essential information about the subject. Therefore commas are required.
You would not use commas if the information defined which James you are talking about. For example, imagine you know two people called James. One (your brother) is a football player and the other (a colleague) is not. You want to tell someone which James is your brother. You might say this:
Peter
The LearnEnglish Team
They put a party together for me , that/which was surprising.
Is using that here correct?
Hello Khaled.,
No, you can't use that in this example. This is because it is a non-defining relative clause; that is only used in defining relative clauses.
Peter
The LearnEnglish Team
How can i know if it is defining or not if there is not comma , and also aren't the writer the one who chooses is this a defining or not , to make it easier to read and understand.
Thank you for replying to the previous comment.