Is it wrong to say "expert of something", not "expert on something"? What's the difference?
Answer from a Native speaker
"Expert of something" should not be used. You can say "expert on something" or "expert in something". You can use "expert on something" to refer to a specific subject one is an expert on. "Expert in something" can be used to describe a field of study one is an expert in. Ex: She's an expert in education. Ex: He's an expert on teaching English.
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