expert       
 noun [ C ] uk/ˈek.spɜːt/ us/ˈek.spɝːt/
B1 专家;内行;行家
a person with a high level of knowledge or skill relating to a particular subject or activity
  a gardening/medical expert 园艺/医学专家 
 My mother is an expert at dress-making (= she does it very well). 我妈妈做裁缝活可是行家。 
 - More examples
 - We need to bring in an expert to deal with this problem.
 - He's an expert on 15th-century Italian art.
 - Bomb disposal experts have defused a 110-pound bomb at Victoria Station.
 - The competition will be judged by a panel of experts.
 - Most medical experts believe that breast-feeding is better than bottle-feeding.
 
expert       
adjective [ before noun ] uk/ˈek.spɜːt/ us/ˈek.spɝːt/
B2 专家的;内行的
having or showing a lot of knowledge or skill
  The centre provides expert advice for people with financial problems. 该中心为大家提供理财方面的专家咨询。 
 What's your expert opinion? 作为专家,你有什么意见? 
 an expert fisherman 一个经验丰富的渔夫 
 - More examples
 - We need expert advice, and that's why we've called you in.
 - A psychiatrist was called as an expert witness for the defence.
 - There is a wealth of expert knowledge to be found in this university.
 - At a time like this you need expert help, not just the help your friends can provide.
 - Could you cast your expert eye over this plan for me, please, and tell me what you think?