Universities, colleges, and technical schools often employ both full-time and part-time faculty. Although the requirements and benefits of teaching at the post-secondary level will vary throughout the world, in the United States, the primary difference between the two is that a full-time faculty member is generally tenured while a part-time lecturer is not. An institution may employ a part-time lecturer to fill a temporary shortage in faculty, to teach a special class not frequently offered, or to supplement the regular faculty.
Most universities and colleges in the United States have a number of full-time tenured faculty in each major offered at the institution. Tenure refers to the employment status reached by the professor where he or she may not be terminated without just cause. A tenured faculty member usually earns more than a part-time lecturer, has additional benefits such as health insurance and a retirement plan, and may have first choice when deciding which classes to teach. On the other hand, a part-time lecturer is usually only hired on a class-by-class basis and has no benefits.
On some cases, accepting a position as a part-time lecturer is a stepping stone to a full-time faculty position. Many aspiring professors start out teaching on a part-time basis and eventually gain the experience and reputation required to be offered a tenured position. Offering an individual a part-time, or adjunct, position is also a good way for the institution to determine whether the prospect is a good fit for a permanent position when one comes open.
Other people choose to teach as a part-time lecturer, or adjunct professor, as a way to make additional money or simply because they enjoy teaching. Many adjunct professors are professionals who are currently working in the field and therefore offer the students firsthand knowledge and insight into the subject matter. Lawyers, for instance, are often asked to teach a specific class in the area of law in which they specialize as it affords the students a unique perspective into the subject area.
An adjunct, or part-time, lecturer is usually only under contract to teach a specific class for a semester at a time. In some cases, an adjunct may teach more than one class, or may return on a regular basis; however, he or she is not guaranteed employment as a tenured faculty member is. Depending on the circumstances, a part-time lecturer may be required to follow an outline and therefore have less freedom to structure the class in a way he or she chooses. If, however, the adjunct was asked to teach due to his or her expertise in the field, this is not usually the case.