English grammar (See all)
MustThe auxiliary verb must can express:
• Obligation, duty, or need to do something:
I must attend this meeting. I have to, I need to attend this meeting.
He must pay his taxes before the end of the month. He is obliged to pay his taxes before the end of the month.
• certainty or a logical conclusion:
It's late, he must be at home now. It's late, so I imagine he is probably at home now.
The hardware works fine, it must be a software problem. The hardware is working perfectly, so I imagine it's probably a software problem.
In its negative form, mustn't always expresses prohibition:
You mustn't talk to strangers, kid. It's forbidden to talk to strangers, kid.
Do you have smart way of remembering this rule? A tip to avoid making a mistake on 'Must'? Share it with us!