An expert, more generally, is a person with extensive knowledge or ability in a particular area of study.

专家，通常意义上讲，是在某一个特定领域拥有渊博的知识或能力的人。

youdao

The core competence of tomorrow's e-commerce successes will be the ability to change quickly, a skill perhaps even more valuable than knowledge of any particular market.

ECONOMIST: In one form or another, electronic commerce is here to stay

Mr. Shakmak said he had no knowledge of a particular threat to Libya, but said Tripoli was sending more troops to the border and to desert oil fields, and boosting communications capacity, as a precautionary measure in response to the Algeria attack.

WSJ: Libya Boosts Oil-Field Security