/mʌst; məst/ aux. （表示必要或很重要）必须；（用于表示肯定推测）一定，谅必；（提出建议）应该；（用于表示意图）一定要，坚持要；（用于表示同情）必定；（用于问句中表示生气）非要 ；（用于感叹句，表示惊讶或震惊）一定是 n. <非正式>必不可少的事物；（发酵前或发酵中的）葡萄汁；潮气，霉菌；（尤指发情期的公象、雄骆驼等的）狂暴状态（=musth） 【名】 （Must）（美）穆斯特（人名） 复数 musts “have to” and “must” are both used to express obligation. To use them correctly, you have to decide where the obligation comes from. MUST for INTERNAL OBLIGATION - the speaker thinks that it’s very important to do something, must is only used in the present. • I must talk to someone. I can’t deal with this on my own. • She’s so thin. She must put on some weight. • You must ask your doctor before going on a diet. • You must see this film. Use HAVE TO to talk about both internal and external obligation in the PAST or the FUTURE. - somebody has told the speaker to do something • ‘What did the doctor say?’ ‘I have to take these pills for a month and do exercise every morning.’ • I have to go and see my son’s teacher. She’s sent me a note. • Sorry, I have to go now. I’ve got an appointment at five. • Do I have to leave a deposit? “I must” is in the present tense and muans you have to do something.