I saw in a textbook,

“He studied the slipperiness of banana peels. (...) He is an expert in medical science.”

I have seen “expert on —-“ many times but this is the first time I saw “expert in —-“.

“Expert on” is understandable for me because “on” is often used like “a book on animals”, which shows that the book is for specialists of animals.

When I looked up the word in a dictionary, the word “expert” is used even with “at” and “with”.

Is there any difference between these combinations?

1 Answer 1


Expert at/in are common and, we can find many examples from authentic sources like dictionaries' sample examples. This means both are correct and it may depend on the writer's style to choose the preposition. Expert on... something is also correct but I think it's not that common. And, so is expert with...

Nevertheless, if I read between the lines, I may prefer using expert in... if I'm talking about some field.

He's expert in medical science

On the other hand, if I'm talking about some procedure/process, I may use *expert at...

He's expert at robotic surgery

Note that this is just my two cents and not a rule.

  • 1
    Your example sentences are good. They show how many native speakers would use in with a subject area and at with a skill.
    – TimR
    Oct 23, 2018 at 10:25
  • 1
    ...and 'on' with a topic: "Italy's top expert on Leonardo da Vinci, died at his villa outside Pistoia on Friday."
    – JeremyC
    Oct 23, 2018 at 21:40
  • @JeremyC Can I make this clear? You mean da Vinci is an object of research in this sentence?
    – Hidechan
    Oct 24, 2018 at 12:15
  • 1
    Yes. That is exactly right. Leonardo daVinci is not a 'subject area' (where 'in' would be right) or a 'skill' (where 'at' might be right).
    – JeremyC
    Oct 24, 2018 at 21:34

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