A boy is a son


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  1. a. A beaver builds dams.
    b. *One beaver builds dams.​
  2. a. *A boy is tall.
    b. One boy is tall.​
  3. a. ?A boy is a son.
    b. ?*One boy is a son.​
I am a Japanese university student studying English linguistics. I am writing a paper and would like help.
3 is a non-sentence and b is a correct sentence?:confused:

Since 1 is the definition sentence after the subject, the indefinite article was used at the beginning of the sentence, and one became non-sentence.
On the other hand, 2 is not the case because all the boys are tall, so I think it will be reversed.
Is 3 in the same way as 1 in the case where 3 is a definition sentence?
  • There is nothing wrong with the English of any of those sentences (six). But some sound very strange and weird in usage.
    Some say things that are not correct; that's not a linguistics matter. e.g. A dog is a fish.

    I don't think it's so complicated "An X" is sometimes used for a whole class of things. NOT a particular thing. "A man has two legs."

    Note this is different from "A man came to my house yesterday."

    The construction "One X" might be generic, but more likely refers to a single thing, in many contexts. Your 2b. (One boy in the class).

    Note that there are other uses of 'one x' as in "One idiot can wreck the whole project." Just one, but not specified.
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    Moderato con anima (English Only)
    English (Singapore/UK), basic Chinese
    Sometimes in linguistics, sentences are presented in isolation and then categorised as grammatical or ungrammatical. I find that some sentences that look strange can work when put into particular contexts.

    For example, I think 3a can work if you are discussing logic. 'What is a boy? Well, a boy is a son.' Or if you are trying to emphasise that boy is also someone's son. 'You might say he's just a boy who deserved what he got. But remember that a boy is also a son. What parent doesn't weep for a son who has strayed?'

    And so on. All the sentences marked with a star or question mark I can imagine being said in a particular context.