must
//mʌst//
modal verb
1
Used to express obligation or necessity; to be required or compelled to do something
I must finish my homework before dinner.
2
Used to express strong recommendation or advice
You must try this restaurant. The food is amazing!
3
Used to express logical certainty or strong probability; to be very likely
She must be tired after working all day.
Noun
1
Something that is essential or absolutely necessary
A good dictionary is a must for language learners.