specialist

/ˈspɛʃəlɪst/noun

A person with deep knowledge or skill in one particular field of study or work.

Example sentence

“Her doctor referred her to a heart specialist for further tests.”

Takes 'in': 'a specialist in tax law'. In medical contexts it means any doctor other than a general practitioner.

Related words

pediatricianA doctor whose specialty is treating babies, children, and young people.midwifeA trained professional, traditionally a woman, who helps mothers during childbirth without being a doctor.psychiatristA doctor who treats mental illnesses and disorders of the mind.paramedicA trained and certified medical worker who treats patients in emergencies before they reach a hospital.radiologistA doctor trained to read X-rays and other medical scans.therapistA person, usually a trained professional, who treats people through some form of therapy.