Doctor
Doctor was an academic title awarded to an individual with a doctorate degree by a university in specific field of study. This title may refer to a Doctor of Medicine (MD) for medical pursuits, or a Doctor of Philosophy (PhD) for scientific pursuits. (; ; ; ) 

Doctors who serve in Starfleet were generally referred to by their title of "doctor" instead of "sir" or their rank.

Richard Daystrom was a doctor in the field of computer science. ()

Types of doctors 
 Astrophysicist
 Dentist
 Engineer
 Physician
 Scientist
 Surgeon
 Veterinarian

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Titles