(2) information about the noun in the sentence,

(2) Restrictive and non-restrictiveRelative clauses are traditionally classified into restrictive (defining) and non-restrictive (non-defining). Both of them are used to give extra information about the noun in the sentence, but not in the same way.         The restrictive relative clause gives detail about the specific noun that is defined, and we generally use a relative pronoun (e.g. who, which, whose, whom and that) in the sentence. While the non-restrictive relative clause gives detail, without restricting the person or thing being mentioned and we use the wh-words in the sentence.         (a)Her sister who works at the supermarket is my classmate. (defining)      (b)Her sister, who works at the supermarket, is my classmate. (non-defining)-Even though they look very similar but have different meanings. (a) means she has more than one sister. The one I’m talking about works at the supermarket; while (b) means she has only one sister, and that sister works at the supermarket.         The information in a restrictive relative clause is important, so we can’t omit the relative clause, while the information in a non-defining relative clause is not necessary to the meaning of the sentence, so we can omit it. For example:         (a)The student who is sitting next to me is my friend.         (b) The River Nile, which is over 6,500 kilometres long, is Egypt’s main source of water.-without the information in (a), we do not know which student the speaker is referring to; while it is clear which river in (b), so that the relative clause is extra information.Furthermore, for the restrictive relative, it can question the head noun with ‘which’:         Which city is larger than London?The relative pronoun can be omitted when the restrictive relative clauses have the gerund-participial clause correspondence, it can be called ‘reduced relatives’:         The man (who) drinking orange juice is my friend.we can use the subordinator that instead of who, whom or which in restrictive relative clauses, but not in non-restrictive relative clauses:         They’re the people who/that want to buy our house.         The car, which was very old, was bought by John ten years ago.         *The car, that was very old, was bought by John ten years ago.we can omit the relative pronoun when it is the object of the verb in the restrictive relative clause, but not in non-restrictive relative clause:         This is the book (which) I told you about last week.         The child, who I play with, is running on the playground.         *The child, I play with, is running on the playground.For the non-restrictive relative clause, it can include the sentential (also called connective) relatives. It is referred to the whole preceding clause or sentence, rather than to the preceding noun.         He kept on making lots of noise, which annoyed all of us(=…noise; this annoyed….)         Sherry doesn’t want to meet Peter, which I can understand and imagine.