1. such as = like,都视为介词,其后加名词、代词和动名词等,一般列举不完全的多例,且和举例之间直接相连.
如：I have many friends, such as / like Tom, Mary and Jim.
2. for example = for instance,视为独立成分,一般只列举一例,和举例之间用逗号隔开,例子形式多样,可以是单词、短语或句子.
如：I have many friends. For example/instance, Jack is my best friend.
3. as if是连词,引导方式状语从句或表语从句.有时其后的从句可以用省略语法,且有时须用虚拟语气.
如：He spoke as if he knew everything.
It seemed as if it was going to rain.
4. as if的意思是“似乎、好像”,是作比喻；
而最开始的两种单词短语的意思都是“例如,比如”,不是作比喻,而是举例.
两组短语在意思上差别很大.
