If you've taken an entry-level college course, chances are, you were taught by an adjunct, part-time lecturer, or instructor.

A graduate teaching assistant (GTA) is similar to an adjunct instructor, with one key difference. The teachers filling these roles are students themselves, enrolled in a master's or doctoral program.

A visiting professor (or scholar, researcher, fellow, or lecturer — once again, the terminology varies by institution and department) is an academic from one school who temporarily works at another school. A college or university might hire a visiting professor to offer a new perspective to its students, host a collaboration between teachers and researchers, or temporarily fill a vacancy in a department. Typically, a visiting professor stays at the school they're visiting for several months to a year.

hough the title might imply otherwise, assistant professors are typically full-time college or university faculty members who teach a variety of courses and conduct research. An assistant professorship is typically the first step on the path to tenure. For that reason, these jobs are usually very competitive and held by individuals with doctorate degrees. Typically, hundreds of people apply for a single tenure-track, assistant professor position.

Associate professors are a little further along in their tenure-seeking journeys than assistant professors. (Note: it's important to realize that this title has different meanings in other parts of the world. In the US and North American academic systems, an associate professor is in a tenure-track position between assistant and a full professorship, but in other countries, it may carry slightly different hierarchical implications.)

Full professors are the next level of a tenured professor. Usually, after associate professors receive tenure, they will be up for a subsequent review after five to seven years in the role. This is to assess one's qualifications for full professorship. Full professor is the highest promotion that a tenure track professor can receive, other than special distinctions like endowed and distinguished professors. Like the other tenured professors on this list, you can usually call full professors "Dr." or "Professor," depending on whether one has or has not earned a doctorate. Typically, full professors will teach higher-level undergraduate and graduate courses. They are also likely to be involved in leadership positions in their department or school.

To understand what an endowed professor is, one must first understand the meaning of an endowment. A university endowment is a sum of money given to the school to be invested. The interest and dividends from the invested donation give the school money to operate on, while the initial amount remains secure, ensuring sustainable financial support. An endowed professor is one whose salary is funded through an endowment. An endowed professor — whose position is often called an endowed chair or professorship — is typically an honoured and esteemed faculty member. Often the position is named for the donor who gave the endowment to fund the professorship, and sometimes the endowed professor is someone who is carrying out research or instruction that aligns with the donor's philosophy, vision, or passion. Unless told otherwise, you can call an endowed professor "Dr." or "Professor."

Distinguished professor" is a title sometimes given to the top tenured professors in a university, school, or department. Distinguished professors are usually awarded this title because they are highly regarded and seen as a leader in their field of study. Some schools have their own title for a distinguished professor, like Yale University's "Sterling Professor" title or MIT's "Institute Professor" award. Like the other tenured, doctorate-holding professors on this list, you can typically address a distinguished professor with "Dr." or "Professor." If you're taking a class with a distinguished professor, congratulations! Take the opportunity to learn from and engage with a person who's at the top of their field. And if you're aspiring to distinguished professorship someday, best of luck. It will likely be a long, but rewarding and exciting journey

How do you get a job as a college or university president? Usually by working as a professor at first. Many school administrators — presidents, provosts, deans, etc. — begin their careers as professors and then work their way up to an administrative position. Often schools choose administrators who are already working at the college or university, assuming that professors and other faculty members know the school's culture and can offer informed experienced leadership. Though the degree requirements are often the same for teaching professors, research professors, and school administrators, the jobs are quite different. As you study and interact with different professors and administrators, you'll notice that some love to be in the classroom with students, while others prefer writing and research, while still others enjoy leading entire departments, schools, or institutions. If you're aspiring to a career in academia, it's worth taking stock of your strengths, weaknesses, preferences, and passions. This can help you home in on the type of professor or administrator you'd like to be.

A professor emeritus (plural: professors emeriti) is a retired professor who was given the title as an honour upon retirement. Though some professors emeriti continue working part-time at an institution following retirement, many may no longer work actively for a college or university. At some institutions, this honorary title is given to all professors who retire in good standing, while at other schools it requires a special act or vote. Typically, professors are given the title "professor emeritus" regardless of gender, but some organizations will grant retired female faculty the title "professor emerita." Like other professors on this list, you can typically call a professor emeritus "Dr." or "Professor."