(modal auxiliary, defective) To do with certainty; indicates that the speaker is certain that the subject will have executed the predicate.
If it has rained all day, it must be very wet outside.
You picked one of two, and it wasn't the first: it must have been the second.
(modal auxiliary, defective) To do as a requirement; indicates that the sentence subject is required as an imperative or directive to execute the sentence predicate, with failure to do so resulting in a negative consequence.
This door handle must be rotated fully.
You must arrive in class on time.
Еще значения (8)
(modal auxiliary, defective) said about something that is very likely, probable, or certain to be true