a knowledge of ('knowledge' as countable)

eli7

Senior Member
Persian (Farsi)
Is this sentence grammatically correct?

I have a good knowledge of medical topics.

I think because "knowledge" is uncountable, we cannot use "a" before it. But I have seen this form of usage of knowledge a lot.
Can anyone please explain it and say the grammatical point?
 
  • natkretep

    Moderato con anima (English Only)
    English (Singapore/UK), basic Chinese
    Yes, it's correct. I think you have to think of a knowledge of something as a special case. Here is a portion of the usage note from the Macmillian Dictionary:

    Knowledge is sometimes used with a, but only in the pattern a knowledge of something (or a good/deep/thorough etc knowledge of something):
    Effective use of language necessitates a good knowledge of grammar.
     

    eli7

    Senior Member
    Persian (Farsi)
    Thank you. So, if I use "a knowledge of" without the article"a", it won't be a correct form? or both are correct?
     

    natkretep

    Moderato con anima (English Only)
    English (Singapore/UK), basic Chinese
    I think omitting 'a' does not make it ungrammatical, but the meaning might be a little different, and it might sound less idiomatic.

    'I have good knowledge of biology' makes me focus on the knowledge being good rather than something else (say useless​), and even so I would be inclined to change the preposition to 'about'.

    In 'I have a good knowledge of biology', a good knowledge means much knowledge.
     
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