Students attend a lecture by Professor Michael Dubson at the University of Colorado in Boulder earlier this year.

Not everyone who teaches in a college or university is a professor. Many are instructors or lecturers. In fact, not even all professors are full professors. Many of them are assistant or associate professors or adjunct professors.

So what do all of these different academic titles mean at American colleges and universities? Get ready for a short lecture, especially if you are thinking of a career in higher education.

Professors usually need a doctoral degree. But sometimes a school will offer positions to people who have not yet received their doctorate.

This person would be called an instructor until the degree has been completed. After that, the instructor could become an assistant professor. Assistant professors do not have tenure.

Tenure means a permanent appointment. This goal of greater job security is harder to reach these days. Fewer teaching positions offer the chance for tenure.

Teachers and researchers who are hired into positions that do offer it are said to be "on the tenure track." Assistant professor is the first job on this path.

Assistant professors generally have five to seven years to gain tenure. During this time, other faculty members study the person's work. If tenure is denied, then the assistant professor usually has a year to find another job.

Candidates for tenure may feel great pressure to get research published. "Publish or perish" is the traditional saying.

An assistant professor who receives tenure becomes an associate professor. An associate professor may later be appointed a full professor.

Assistant, associate and full professors perform many duties. They teach classes. They advise students. And they carry out research. They also serve on committees and take part in other activities.

Other faculty members are not expected to do all these jobs. They are not on a tenure track. Instead, they might be in adjunct or visiting positions.

A visiting professor has a job at one school but works at another for a period of time. An adjunct professor is also a limited or part-time position, to do research or teach classes. Adjunct professors have a doctorate.

Another position is that of lecturer. Lecturers teach classes, but they may or may not have a doctorate.

And that's the VOA Special English Education Report, written by Nancy Steinbach. You can read and listen to our reports, and get information on how to study in the United States, at voaspecialenglish.com. I'm Barbara Klein.

adjunct professor: 兼職教授，助理教授

tenure: the right to stay permanently in your job, especially as a teacher at a university （尤指大學(xué)教師的）終身職位，長期聘用

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（來源：VOA 編輯：陳丹妮）