musieć

1. to have to, to need to, must (to be obliged to)
2. to have to, to need to, must (to be obliged to)
3. to have to, to need to, must (to be obliged to)
4. (colloquial) to have to, to need to, must (to be obliged to)
5. to have to, to need to, must (to be obliged to)
6. to have to, must; used to indicate certainty

muszy

fly (of, pertaining to, or characteristic of a fly (insect))