关于as与like有什么异同，是中国学生在学习英语过程中常遇到的一个问题。在这里，我们愿意就这个问题谈谈我们的一些认识。
让我们先看看as和like的相异之处，因为，相对地说，二者的相异之处比较明显易懂。由于as可以用作连词、关系代词、副词和介词，所以我们就按此顺序讨论如下：
1. 连词as表时间时，不可代之以like, 如：
(1)As I was going out, it began to rain.
(2)He returned home as I was leaving.
连词as表原因时，不可代之以like，如：
(3)He stayed at home as he was ill.
(4)As the last bus had left, we returned on foot.
连词as表“随着”时，也不可代之以like，如：
(5)As he grew richer he grew more ambitious.
(6)One advances in modesty as one advances in knowledge.
连词as表“虽然”时不可代之以like，如：
(7)Worn out as they were, smiles and satisfaction showed on their faces.
(8)I cannot tell you, father, much as I would like to.
在下面的句子结构中，连词as意谓“如同”，但也不可代之以like，如：
(9)She's musical, as her mother was.
(10)As two is to one, so is twelve to six.
此外，有些固定结构如according as, as...as, so...as, in so far as, in as much as等中的as亦均不可代之以like。
2. 关系代词as不可代之以like，如：
(11)As is announced in today's papers, all the schools will reopen on 15 February.
(12)Such men as heard him praised him.
(13)The present owner is a keen art collector, as were several of her ancestors.
3. as用作副词时不可代之以like，如：
(14)He is nearly as tall as his father.
(15)I can walk as far without getting tired.
4. as用作介词意谓“作为”时不可代之以like，如：
(16)I work as a hotel receptionist.
(17)My duty as a worker triumphed for this reason over my civic conscience. （as a worker=as a worker's duty）
(18)Who's used this knife as a screw-driver?
现在再看看like不可代之以as的情况：
1. like用作动词时自然不可代之以as，如：
(19)I'm hungry, I'd like some hot food.
2. like用作名词时自然也不可代之以as，如：
(20)In New York like seeks like .
3. like用作形容词时也不可代之以as，如：
(21)They are as like as two peas.
4. like用作副词时也不可代之以as，如：
(22)He's an old fellow, like, and he can't, like , walk very far on his own, like.
5. 下面句子中用作介词的like也不可代之以as:
(23)That's just like him. （like=typical of）
(24)What is Shanghai like now? 现在上海的情况如何？
(25)It doesn't look like mine. （与look固定搭配）
(26)It's raining like the devil. （like the devil, like hell, like anything等皆是固定词组）
(27)You mustn't think like that. （like that也是一固定词组）
(28)My first feeling was how very like each other were John Elias and Jocob Stein. （like可与very, most等表程度的副词连用，as则不可）
上面所讲的都是as与like不可相互代替的相异之处。下面让我们看看as与like有何相同之处，以及在什么情况下二者可以相互代替。
as与like的相同处或可相互代替之处多表现在二者皆用作介词并皆意谓“像”或“如同”之时。这种情况大致可分为下列四类：
1. as与like皆可用在系表结构中，如：
(29)His face was as a mask of gauze through which nothing was quite clearly visible.
(30)The shock to me was as that of a thunderbolt.
(31)The people no longer came to admire his work; the princes no longer paid him honour or brought him gifts: and he became as one forgotten in the world.
上述句子中的as皆可代之以like，但as的意思近乎“简直是”，句（31）中的as尤其是这个意思；like则只是意谓“像”而已，而且可被表程度的副词所修饰。另外，as似不及like通俗。
2. as与like皆可用在某些不及物动词之后，如：
(32)Though an ex-serviceman, he lives as a man in active service.
(33)We lived and fought among the people as “fish in water”.
上面两句中的as皆可代之以like而意义不变。但请注意下面一句中的as虽与like同义，却不可代之以like：
(34)All rose as one man. （as one man或as one已成为固定词组，故不可代之以like）
3. as与like有时也可用在“及物动词+宾语”之后，如：
(35)He treats his wife as a child. （或用like）
亦可用在这种句子的被动结构中，如：
(36)He was dressed as a woman. （或用like）
4. 在同位结构中，有时用as或like均可，如：
(37)Some animals, as dogs and cats, eat meat. （亦可用like。as在此相当于such as）
当as和like同作连词而且意义相同（皆意谓“如同”）时，二者一般皆可相互替代，如：
(38)Like I told you, it's an offer I can't refuse. （=as）
(39)Do it like I do it. （=as; like I do it也可改作like me）
(40)We can't have everybody talking at once. We'll have to have “Hands up” like at school. （=as at school）
顺便提及，连词like还可以用来代替as if，如：
(41)It looks like he's feeling sick.
(42)She's spending money like there was no tomorrow.
但请注意上述句中的连词like只用在非正式文体中，尤多用于美国英语。最后，请注意下面各对句子中as与like的不同意义：
(43)He acts as a teacher. （意为他本人是一位教师）
He acts like a teacher. （意为他本人不是一位教师）
(44)They talked as old friends. （意为他们是老朋友）
They talked like old friends. （意为他们不是老朋友）
(45)He died as a hero. （意为他作为英雄而死去）
He died like a hero. （意为他英雄般地死去了）
(46)He treats me as an intimate friend.（意为我是他的密友）
He treats me like an intimate friend. （我不是他的密友）
