I- Special verbs  1. Auxiliary verbs (Helping verbs - Trợ động từ) BE (is / are / am / was / were / been) DO (does / did) HAVE (has / had) 2. Modal (Defective) verbs (Động từ hình thái - Động từ khuyết thiếu) CAN (COULD), MAY (MIGHT), SHALL (SHOULD), WILL (WOULD), MUST, NEED, DARE, USED (to), OUGHT (to) Necessity (cần thiết): must, have (got) to, needn’t and mustn’t Ex: I must go to school. Obligation (bắt buộc) and advice (khuyên bảo): should, ought to Ex: You should read this book. Permission (xin phép) : can, could, may might and be allowed Ex: You can walk on the grass here. Certainty (sự chắc chắn): will, must and can’t Ex: Nam must be Vietnamese. Probability (có lẽ): should and ought Ex: The rain should stop soon. Possibility (có thể): may, might, can and could Ex: The students may be in the library. Ability (khả năng): can, could and be able to Ex: Nam can swim in the river. Unreal situations: (tình huống không thật) : would Habits (thói quen): will, would and used to Challenge (thách thức) : dare 3. Modal verbs in the past Modals verbs + have + Past participle Ex: You should have worked harder. (Lẽ ra bạn nên học chăm hơn) Ex: Nam must have won the first lottery. (Hẳn Nam đã trúng sổ độc đắc) 4. Modal verbs a) No ending -S:  Ex: He speaks Chinese very well. b) Not followed by TO:  Ex: He wanted to go out last night.                                           Exc.: He ought to help his friends. c) Interrogative form:  Ex: Do you speak French well?                                     Ex: Have you been to Hanoi? d) Negative form: Ex: He didn’t go shopping last week. II - Ordinary verbs 1. Vordinary → (past & Past Participle) + ED 2. Vordinary in Negative & interrogative, we must use the auxiliary DO (DOES/DID) is.