A relative clause is a type of subordinate clause that gives additional information about a noun in the main clause. For example, we can take a simple sentence like 'The book is interesting' and expand it by adding a relative clause. The expanded sentence becomes 'The book that I bought yesterday is interesting.' Here, the main clause is 'The book is interesting' and the relative clause is 'that I bought yesterday' which gives us more information about which book we're talking about.
Relative pronouns are the words that connect relative clauses to the main clause. The main relative pronouns are who, whom, whose, which, and that. WHO is used for people as the subject of the clause, like 'The student who studies hard will succeed.' WHICH is used for things and animals, as in 'The book which I borrowed is interesting.' WHOSE shows possession, like 'The teacher whose class I attend is kind.' WHOM is used for people as the object, and THAT can be used for both people and things in many situations.
There are two types of relative clauses: defining and non-defining. Defining clauses give essential information that identifies which person or thing we're talking about. They don't use commas. For example, 'Students who study hard pass exams' - here we're specifically talking about students who study hard, not all students. Non-defining clauses give extra, non-essential information and must be separated by commas. For example, 'My students, who study hard, pass exams' - here all my students study hard, and this is just additional information.
The position of relative clauses is crucial for clear communication. A relative clause must come immediately after the noun it describes, which is called the antecedent. For example, in 'The book that I bought is on the table,' the word 'book' is the antecedent and 'that I bought' is the relative clause that describes it. Always keep relative clauses close to their antecedents to avoid confusion. A misplaced modifier can change the meaning completely, like saying 'I saw a dog walking to school that was very big' - this suggests the school was big, not the dog!
Now let's practice with some questions. Question 1: The man who called yesterday is my uncle. The answer is A, who, because we use 'who' for people as the subject. Question 2: This is the book that I told you about. The answer is B, that, because 'that' can refer to things. Question 3: The girl whose bag was stolen reported to police. The answer is C, whose, because 'whose' shows possession. These practice questions help reinforce the rules we've learned about relative clauses and their proper usage in English grammar.