A professor is a teacher at a college or university who has earned advanced degrees and specializes in a particular subject. Unlike teachers in elementary or high school who might teach several subjects, a professor focuses deeply on one field: maybe chemistry, history, literature, or mathematics. They spend years studying their subject, often earning a PhD (a high academic degree), before they can become professors.

Professors teach classes and conduct research to discover new knowledge in their field. A biology professor might study new medicines, while a history professor might uncover forgotten details about ancient civilizations. They write books and articles sharing what they've learned, and other scholars around the world read and debate their ideas.

Becoming a professor requires both deep knowledge and the ability to explain complex ideas clearly and inspire students to think critically about the world.

Students in college often call their teachers “Professor Smith” or “Professor Johnson” as a sign of respect for their expertise and achievements. The informal term prof is sometimes used among students, though usually not to the professor's face.