1. Nếu trong mệnh đề quan hệ có giới từ thì giới từ có thể đặt trước hoặc sau mệnh đề quan hệ (chỉ áp dụng với whom và which.)

Ví dụ: Mr. Brown is a nice teacher. We studied with him last year.

=> Mr. Brown, with whom we studied last year, is a nice teacher.

=> Mr. Brown, whom we studied with last year, is a nice teacher.

 

2. Có thể dùng which thay cho cả mệnh đề đứng trước.

Ví dụ: She can’t come to my birthday party. That makes me sad.

=>  She can’t come to my birthday party, which makes me sad.

 

3. Ở vị trí tân ngữ, whom có thể được thay bằng who.

Ví dụ: I’d like to talk to the man whom / who I met at your birthday party.

 

4. Trong mệnh đề quan hệ xác định , chúng ta có thể bỏ các đại từ quan hệ làm túc từ:whom, which.

Ví dụ: The girl (whom) you met yesterday is my close friend.

The book (which) you lent me was very interesting.

 

5. Các cụm từ chỉ số lượng some of, both of, all of, neither of, many of, none of … có thể được dùng trước whom, which và whose.

Ví dụ 1: I have two sisters, both of whom are students.

She tried on three dresses, none of which fitted her.

Ví dụ 2: Daisy has three brothers. All of them are teachers.

---> Daisy has three brothers, all of whom are teachers.

Ví dụ 3: He asked me a lot of questions. I couldn’t answer most of them.

---> He asked me a lot of questions, most of which I couldn’t answer.

 

6. KHÔNG dùng THAT, WHO sau giới từ.

Ví dụ: The house in that I was born is for sale.