They are basically the same when used in positive sentences: however, we generally use "must" for things you tell yourself are important to do ("I must send my mother a birthday card this week") and "have to" for things that are rules from other people ("You have to wait for the light to turn green before you can cross the street"). When used in negative sentences, "must not" means the opposite of "must," but "don't have to" isn't the opposite of "must"—instead, it means "not necessary." So we can say, "You must not drink and drive" but "You don't have to drink and drive" is NOT correct. A correct use of "don't have to" would be, "I don't have to wake up early tomorrow, because it's a holiday."

Someone asked about have to and must yesterday. This is a copy of the answers: Are these two sentences right or wrong ? What say the rule ? 1. You have to be quiet in the libray. 2. You musn´t take photopraphs inside the museum. It´s not allowed. For learning: English Base language: English Category: Language Share: Share on twitterShare on facebookShare on google_plusone_shareShare on emailMore Sharing Services 0 Luis 15 hours ago 1 answer 24 views Flag 0 comments Answers Sort by: They are both correct. "Have to" is more common. "Must" has more emphasis so if you want someone to do something "must" makes it sound more important. Note: In your question, you wrote "What say the rule?" That should be, "What does the rule say?" or even simpler, "What is the rule?" 2 Kelly Torza 15 hours ago 4 comments - Add a comment Flag Show previous comments Kelly Torza 14 hours ago No problem! That happens to me all the time in Spanish. Su.Ki. 11 hours ago Luis, can I give you another tip about 'must' and 'have to'? If you want to ask a question, it is best to use 'have to' rather than 'must'. eg 'Do I have to use a password?' is much more common than 'Must I...' Also, it is important to remember that the negative of 'must' is 'don't have to' (NOT 'mustn't') . As you correctly said in your example above, 'mustn't' means something is not allowed. eg You have to take off your shoes when you go into a mosque (necessity) You must take off your shoes when you go into a mosque (necessity) You don't have to take off your shoes when you go into a church (it's not a necessity. I hope that's useful. Kelly Torza 6 hours ago Su.Ki., good point