as 和 like 在汉语中都译做"像",但字面下的隐含意思是不同的.
like侧重A B两者间的比较,并不意味着A和B属于一类或完全相似.
例如:He speak English like an Englishman.(=in a way an Englishman
speaks English.)
表示有些相象
as则侧重于同一性,意味着A B两者属于同一类或完全相似.
例如:He speaks English as an Englishman.(=as well as an English.)
表示讲得一样好

as与like是英语中常见的两个词,他们的语义和用法很多.在语义上者两个词都可以当"像......","正如......"讲,说明人与人、物与物、动作与动作、状态与状态之间的相似之处。但其语法结构却是不一样的。
一、当“像”讲时，语法结构的不同之处是：
1、as作连接词。她引导比较状语从句和方式状语从句，而且这两种从句通常为省略句。例如：
1、She is a fine singer, as her mother used to be.
2、There is as much water in this cupas in that one.
2、like作介词。例如：
3、My sister isn''t much like me.
4、The robot can''t work like man.
如果需要加强语气，再这两个词之前加上just之类的词即可。例如：
5、All the plants and animals need air just as they need water.
6、Mary goes to school at seven every morning just like her brother.
含义不同之处是：
(1)like只是单纯表示比较，而且通常不是同类事物进行比较：
7、The ship looks like a high building.
8、The sky was like ink over my head.
(2)as可表示同类事物比较。
9、This ship is as long as that one.
二、当“正如....”意义讲时，语法结构的不同之处是：
(1)as作关系代词或关系副词、引导定于从句。
as 在这样的句子里指全句所谈到的内容，引出非限制性定于从句，在从句中一般做主语或宾语。例如：
10、Metals have many good properties, as has been stated before.
11、As we said before, you have done a good job.
(2)like作界词。
12、She, like thousands of others, is fascinated by this work.
三、as与like有时可以换用。
(1)在非正式的美国英语中like可用作连词，代替as.例如：
13、Nobody loves you like I do, baby.
(2)在非正式的文体中，like，常被用来代替as if.
14、Duke said:"You feel like you could reach out and touch it (the space)."
四、as常用于下列词组：在as you know ,as we agreed, as you suggested 这些词组中，as的实际意义不是比较，也不是相似，而是同一事物或人之义。例如：
as you know 的意思不是you know somthing like this ,而是you know this.
15、As he knew, she wasn''t much at letter-writing.
16、As all his friends agree, he was unusually warm-hearted,loving and generous.
在非正式问题中，有时可以在这种词组里用like,但在受过教育的人所使用的英语中不多见

但是OG68中Often visible as smog,的AS是什么用法？不是也连接名词表示相象了吗？并且二者不算同类吧

thanks !!!!