Must
[obligatie sau datorie] You must do your homework if you want to get good marks.
[necesitate] She must go to the doctor, she's been coughing for three days.
[certitudine] It must be really cold outside; it's snowing.
Mustn't
[prohibition] You mustn't cross the street on the red light.
[negative obligation] She mustn't use her cellphone during the meeting.
