A medical doctor who specializes in the study of mental and emotional issues or problems: It takes many years of advanced medical studies to become a psychiatrist.

A person who has studied the mental and behavioral characteristics of individuals, but who does not have a medical degree: As a psychologist, Jerry's sister works in schools where there are children who have emotional problems.

1. An individual who has been trained to understand how the mind influences the behavior of people and who has studied and been trained to understand the way the brain influences the behaviour of individuals who may have mental and emotional problems: The psychometrician was very good with young children and gained their cooperation during the testing procedures.
2. A person who has been educated to understand how the mind influences the behaviour of people and who deals with the design, administration, and interpretation of quantitative tests of intelligence, aptitude, and personality traits: Tracy had a psychometrician who provided an evaluation of her son who was having problems adapting to relationships with other people.

Someone who treats people with mental and emotional disorders: The psychotherapist who worked with Dennis provided healing procedures that helped him to achieve more self-control over his excessive reactions of anger.