1、情态动词情态动词的类型1)只作情态动词的有：must,can(could),may(might),ought to2)可作情态动词也可作实义动词的有：need,dare3)可作情态动词也可作助动词的有：shall(should),will(would)4)具有情态动词的某些特征的有：have(had)to,used to情态动词的特征1)有一定的词义，但不能单独作谓语，要和动词原形连用构成谓语。2)适用于主语的各种人称和数 We/He/You must study hard.3)后面接动词原形。He may lose his way.4)具有助动词的作用，即可用来构成否定句、疑问句及用于简略答
2、语。I cant swim.Can you swim?Yes,I can.表能力表能力can表示主体内在的或本身具有的能力。用于一般现在时。could表示主体内在的或本身具有的能力。用于一般过去时。I can read this sentence in English.He could eat two bowls of rice when he was five years old.be able to 表示过去特定的能力或经过努力才具备的能力。可用于多种时态。He was able to write in English after years of practice.表请求表请求/建议建议
3、can&could疑问句中表示请求。could比can语气更委婉。may/might疑问句中表示客气请求。might比may语气更委婉。Can/Could you give us a hand?May I come in?Shall.?用于第一、三人称，表示建议或请求。Shall we ask the teacher for help?表请求表请求/建议建议Will/Would.?用于第二人称疑问句，表示征求意见或提建议。Will/Would you please take out the trash?表命令或义务表命令或义务must表“必须”mustnt 禁止,不允许 dont have t
4、o 不必须 neednt do dont need to must着重说明主观看法，have to 强调客观需要。另外，have to 能用于更多时态。I dont like this TV set.We must buy a new one.Mother was out,so I had to look after the shop.mustvshave to表命令或义务表命令或义务注意对need和must 问句的回答：-Need I finish the work today?-Yes,you must.-No,you neednt.-No,you dont have to.-Must w
5、e do in now?-No,you neednt.表命令或义务表命令或义务表命令或义务表命令或义务should/ought to 应该，表示“劝告，责任，建议，义务”You should take care of your family.will/would表示个人主观意愿和决心。I will help you at any time.I will never do that again.表祝愿表祝愿May表示祝愿。May you happy!表可能性表可能性可能性的强弱层次：mustshould/ought tocan/couldmay/mightmust 表示推测1.可能性最强，只能用
6、于肯定句eg.That must be my pen.2.must-很可能 cant-不可能eg.That cant be my pen.should/ought to 表示推测1.根据经验的推测，“应当、应该”eg.You photos should be ready by 12:00.2.表示“竟然”，带有感情色彩。eg.It is strange that you should like him.can/could 表示推测1.常用于否定句或疑问句eg.You cant be hungry already-you had lunch only two hours ago!2.can用于肯定句中表示理论上的可能性，并不牵涉是否真的会发生。eg.You can hurt yourself if you play in the street.表可能性表可能性may/might may/might 表示推测1.can not 不可能 may not 可能不2.may well“极有可能”eg.Liza may well not want to go on the trip.-she hates traveling.3.may/might as well“不妨”eg.You may as well stay for dinner.表可能性表可能性
