高中英语语法:弄清三组情态动词的用法区别
温馨提示:以下所讲的几组情态动词的用法区别,是学好情态动词的最基础的知识,学好它,不仅有助于你做好情态动词单项填空题,而且还有助于培养你的英语语感和提高写作的准确性。
1. must 与 have to 的区别
(1) 强调重点不同:两者都表示必须,但 must 侧重于说话者的主观看法,认为有必要或有义务去做某事;have to 则重于客观需要,含有不得不或被迫之意。
(2) 时态形式不同:一般说来,must 只有现在时一种形式(在宾语从句中可以表示过去),而 have to 则有多种时态形式。
(3) have to 可以有分词、动名词、不定式等形式,而 must 则没有这些形式。如:
I regret to have to trouble you again. 我很抱歉不得不再麻烦你一次。
I only saw her in the evening, having to be away all day. 我因整天得外出,所以只能晚上见到她。
(4) 否定式的含义不同:must 的否定式 mustnt 意为不准不允许;而 have to 的否定式 dont have to 意为不必(= neednt)。
2. can 与 be able to 的区别
(1) be able to 可用将来时态表示某人将来才具备的能力,而 can 不能用于将来时态。但若表示现在决定将来是否有能力做某事,可用 can。如:
I can finish the article tomorrow. 我可以在明天写完这篇文章。
(2) be able to 的过去式可表示某人过去某种具体的能力(即在某一具体场合做某事的能力,往往暗示经过努力才具备的能力),但此时不能用 could)。如:
He worked very hard and was able to pass his examinations. 他学习很努力,所以考试及了格。
注:在否定句中 was (were) able to可用 couldnt代替。如:
He worked very hard but wasnt able to [couldnt] pass his examinations. 他学习很努力,但考试却未能及格。
(3) be able to 不仅有多种时态形式(通常不用于进行时或与 be going to 连用),而且还可以与某些情态动词连用 (通常不与 can 连用),甚至还可以有非谓语形式。如:
He has not been able to go to school for a week. 他已有一周不能上学了。
You might be able to persuade him. 你也许能够说服他。
I hope to be able to do the work. 我希望能干得了这项工作。
I regret not being able to help her. 我很遗憾未能帮助她。
3. cant 与 may not 的用法区别
(1) cant 有两个意思:它若表示能力,cant 意为不能;它若表示推测,cant 表示不可能。如:
I cant finish it in time. 我不能按时完成。
He cant be so rich. 他不可能那么富有。
(2) may not 也有两个意思:它若表示许可,may not 表示不许可不可以;它若表示推测,may not 表示可能不。如:
Visitors may not feed the animals. 参观者不得给动物喂食。
He may not be able to help but theres no harm in asking him. 他可能帮不了忙,但是求他一下倒也无妨。 高中英语语法:弄清三组情态动词的用法区别
温馨提示:以下所讲的几组情态动词的用法区别,是学好情态动词的最基础的知识,学好它,不仅有助于你做好情态动词单项填空题,而且还有助于培养你的英语语感和提高写作的准确性。
1. must 与 have to 的区别
(1) 强调重点不同:两者都表示必须,但 must 侧重于说话者的主观看法,认为有必要或有义务去做某事;have to 则重于客观需要,含有不得不或被迫之意。
(2) 时态形式不同:一般说来,must 只有现在时一种形式(在宾语从句中可以表示过去),而 have to 则有多种时态形式。
(3) have to 可以有分词、动名词、不定式等形式,而 must 则没有这些形式。如:
I regret to have to trouble you again. 我很抱歉不得不再麻烦你一次。
I only saw her in the evening, having to be away all day. 我因整天得外出,所以只能晚上见到她。
(4) 否定式的含义不同:must 的否定式 mustnt 意为不准不允许;而 have to 的否定式 dont have to 意为不必(= neednt)。
2. can 与 be able to 的区别
(1) be able to 可用将来时态表示某人将来才具备的能力,而 can 不能用于将来时态。但若表示现在决定将来是否有能力做某事,可用 can。如:
I can finish the article tomorrow. 我可以在明天写完这篇文章。
(2) be able to 的过去式可表示某人过去某种具体的能力(即在某一具体场合做某事的能力,往往暗示经过努力才具备的能力),但此时不能用 could)。如:
He worked very hard and was able to pass his examinations. 他学习很努力,所以考试及了格。
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