- a person who has special skill or knowledge relating to a particular subject
- a computer expert
- She was an acknowledged expert on/in child development.
- an expert at planning dinner parties
- We received some expert advice.
- an expert poker player
- an expert opinion
- The company has become expert at/in adapting its products for new clients.
- expert testimony
- an expert witness [=a witness in a court of law who is an expert on a particular subject]