An adjunct professor is a part-time professor who is hired on a contractual basis, rather than being given tenure and a permanent position. Many universities have chosen to hire large numbers of adjunct faculty because they are flexible and cheaper to maintain than traditional full time faculty members. Just like regular faculty, an adjunct professor must fulfill basic educational requirements before he or she can teach, and many adjunct professors are very well educated, talented people.

For a university, there are a number of advantages to hiring an adjunct professor. Because an adjunct professor is viewed as temporary, for example, a university can hire a part timer for a single semester to expand its course offerings or to meet student demand for a program which does not have enough staff. Because adjunct professors do not have tenure or other rights, a university can also easily get rid of a professor who does not perform to the university's standard: all the school has to do is decline to renew the professor's contract.

In addition to being essentially disposable in the eyes of many educational institutions, adjunct faculty are also much less costly to hire. They are not entitled to benefits such as health care and retirement plans, and they are usually not given offices. Adjunct professors who do have office space typically have to share the space with other faculty. Most are paid by the unit, and their teaching loads vary from part-time to overloaded.

From the point of view of an adjunct professor, there are certainly a number of disadvantages to this kind of work, as detailed above, but there are also some benefits. The same flexibility which allows a university to easily dispose of unwanted professors allows adjunct professors to depart after a term if they are offered better work. They also do not have administrative duties, meaning that they do not need to attend faculty meetings and similar events, and most are not required to perform research or to publish work unless they are interested in seeking full time work. Some people actually prefer working as adjunct faculty because they enjoy teaching, but dislike the academic rat race associated with tenure and full time responsibilities.

The use of adjunct professor positions has grown in many universities in response to decreased funding which forces these schools to make choices which are sometimes difficult. Most people agree that while adjunct professors can be abused, if the choice is hiring adjunct professors or closing a program, it's better to hire the part-time staff.