区别是：
look作行为动词时，可以独立作谓语，意思就是看，观看。
例如：You've just got to look at the last bit of Act Three.
你只要看一下第3幕最后那部分。
look作系动词时，后跟形容词，构成系表结构。行为动词需用副词来修饰。意思是看起来，看上去。
例如：Father looked angrily at my school report.
爸爸生气地看着我的成绩报告单.
look可用作
不及物动词、及物动词和
连系动词。现将其用法归纳如下:
1. 用作不及物动词,意为“看,望,瞧”。
1)单独使用时,后不跟介词。如:
I looked but saw nothing.我看了,但什么也没看见。
Look! Here comes the bus. 瞧!汽车来了。
Look before you leap. 三思而后行。
2)和at连用。如:
The teacher is looking seriously at us.老师正严肃地看着我们。
Look at these pictures. How beautiful they are!看这些画,它们是多么漂亮啊!
3)和其它某些介词或副词连用:
(1) look after 照看,照料。如:He is old enough to look after himself.他年龄足够大,能照看自己。
(2) look for 寻找。如:I looked for you just now, but I didn’t find you.刚才我到处找你,但没有找到。
(3) look around 四下环顾;到处寻找。如:He looked around but he saw nobody.他四下环顾,但什么人也没看到。
(4) look back on回想,回顾。如:They often look back on the days they spent together. 他们常回顾他们在一起度过的日子。
(5) look down on看不起。如:Don’t look down on others.不要看不起别人。
(6) look forward to 盼望。如:We are looking forward to seeing you again.我们盼望再见到你。
(7) look into朝……里面看。如:He looked into the box, but he saw nothing.他朝箱子里面看了看,但没看到什么。
(8) look on...as把某人看作。如:We look on him as our friends.我们把他看作我们的朋友。
(9) look out当心。如:Look out! Don’t hit the tree. 当心!不要撞了树。
(10) look over仔细检查;翻阅。如:The doctor is looking him over. 医生正在给他做仔细检查。
(11) look through浏览;仔细检查;看穿。如:I have looked it through.我已把它仔细地看了一遍。
(12) look up抬头看;查;找出。如:He looked up and smiled at me.他抬起头,对我笑了笑。If there are words you don’t understand, look them up in the dictionary. 如果你有不认识的单词可以查词典。
2. 用作连系动词,意为“看起来”。
1)后跟形容词。如:You look well/fine/healthy.你看起来很健康。The teacher looks happy. 老师看上去很高兴。She looks pale. 她面色苍白。
2)后跟
过去分词。如:You look tired; you’d better have a rest.你看上去很累,你最好休息一下。
3)后跟名词。如:He looks a nice, honest man.他看上去是个诚实的好人。
4) 后跟
介词短语等。如:He looks in good health. 他看来十分健康。
3. 用作及物动词,意为“看,瞧,打量”等。如:He is looking me up and down.他上下打量着我。