Summary of the Most Important in English

Modals and related verbs
1. We use must and have to to talk about necessity. (I must get up early tomorrow)
2. We use mustn’t to talk about prohibition. (You mustn’t take it personally)
3. We use should and ought to to talk about duty or give advices. (You ought to try those shoes first.)
4. We use can or could to talk about ability to in the present or past. (I can go to 0 to 100 in 5,28 seconds)
5. We use can to talk about possibility. (You can still take it back to the shop.)
6. We use can to ask for permission. (Can we join you?)
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