Like focuses on the comparison between a and b, which does not mean that a and b belong to the same category or are completely similar.
He speaks English like an Englishman. In a sense, he is an Englishman.
Speak English. )
Show some similarities
As focuses on identity, that is, A and B belong to the same category or are completely similar.
He speaks English like an Englishman. He is also an Englishman. )
Speak just as well.
In the early days, like was an adjective, meaning similar, identical and similar. As is a conjunction.
Sammy is a lot like Sammy. Sammy and Sammy look alike.
Paul acts like a child. Paul behaves like a child. (Sentence omitted)
Later, like was used as a preposition, meaning like ...; As can also be used as a preposition
Paul acts like a child. Paul acts like a child. (The sentence is not omitted)
Compare again:
Let me talk to you as a father ... let me tell you as a father. I am your father, and I am talking to you as a father.
Let me talk to you like a father .. Let me tell you something like your father. I am not your father, but I am talking to you in your father's way.
Later, some grammarians changed the previous rule that "like" was not allowed to be used as a conjunction and used it instead of "as" in adverbial clauses.
I can't sing like before .. I can't sing like before. (of the timbre of singing)
He writes as his brother did when he was young. His writing style is the same as that of his brother when he was young. (Calligraphy Style and Font)
Even so, like and as are sometimes different. Try to compare:
The priest became like a murderer. The prisoner was hanged like a murderer.
The prisoner was turned into a murderer. The prisoner was hanged as a murderer. The prisoner is a murderer.
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