Beware of anyone who is not a medical doctor but nonetheless refers to him- or herself as “doctor.”

Some people will tell you that if they have a doctorate in something, they’ve earned the right to be called doctor. If that was true, you’d witness a lot more conversations like this:

(MAN, bleeding from a gaping wound in his head, runs up to WOMAN on a crowded city street.)

MAN: “AaaaAAARRHGhghghh!! I need a doctor!”
WOMAN: “I wrote a dissertation on Kierkegaard and the meaning of meaning.”
MAN: “Oh, thank goodness!”

And this:

(TEACHER bursts into university faculty lounge, where THREE PEOPLE are reading.)

TEACHER: “Help! I need a doctor right away!”
PERSON 1: “I’m a neurosurgeon.”
TEACHER (nervously): “Uuuuhmm.”
PERSON 2: “I’m a gastroenterologist.”
TEACHER (sweating): “I — I’m sorry — I just —”
PERSON 3: “What is it?”
TEACHER: “I need someone to talk to about 16th-century French literature for the next eight hours!”
PERSON 3: Oh, a doctor. Try the fourth floor.

In 21st century English, “doctor” means medical doctor. People who adopt the title without first going to medical school are bullshitting you (and possibly also themselves).