Intermediate Grammar
Master English grammar one unit at a time. Clear notes, then 40+ interactive exercises with instant feedback — based on the topics in English Grammar in Use (Intermediate).
Must, mustn’t and needn’t“must · mustn’t · needn’t · needn’t have done” — 44 interactive questions
📖 Grammar Reference — Must, mustn’t and needn’t
Study the notes, then work through the six exercises.
A must and mustn’t
must do something = it is necessary that you do it. mustn’t do something = it is necessary that you do not do it (so don’t do it).
| must | necessary to do | We’re nearly out of time — we must hurry. |
| mustn’t | necessary NOT to do | This vase is fragile. You mustn’t drop it. |
💡 mustn’t = must not. The verb after it is the plain base form: mustn’t be, mustn’t forget — never mustn’t to be.
B needn’t and don’t need to
needn’t do something = it’s not necessary to do it (but you can if you like).
💡 We say don’t need to do / doesn’t need to do (with to), but needn’t do (without to).
C mustn’t vs needn’t
These look similar but mean completely different things:
| mustn’t | not allowed — it is forbidden | You mustn’t park here. (= don’t park here) |
| needn’t | not necessary — but you can if you want | You needn’t book a seat. (= you can if you like) |
D needn’t have done vs didn’t need to do
needn’t have done = you did it, but now we know it wasn’t necessary.
| needn’t have + done | did it — it was a waste | The hall was empty. We needn’t have booked seats. (we booked — no need) |
| didn’t need to + do | it wasn’t necessary | I didn’t need to cook — there was plenty of food. (so maybe I didn’t) |
Made with care for English learners · allenglish4u.com
Original practice material inspired by the English Grammar in Use syllabus (Cambridge University Press). Example sentences and exercises are written by All English 4U.