Traditionally, Assistant Professor has been the usual entry-level rank for faculty on the “tenure track“, although this depends on the institution and the field. Then, promotion to the rank of Associate Professor usually indicates that a tenure-track professor has been granted tenure at the institution. Those hired as Assistant Professors on a traditional tenure track will usually attain the rank of Associate after six to a maximum of eight years, or their employment will be terminated at most universities (so-called “up or out”). It is usually another six to ten years before an Associate Professor can be considered for promotion to “full” Professor.
Traditionally for “professional” fields such as law, medicine, business, or engineering – and lately expanding to others – faculty types can also include Clinical Professor or Professor of Practice. These ranks are generally not tenure-track and emphasize professional practice knowledge/skills rather than scholarly research. Likewise for the less-common title of Teaching Professor, which is not limited to professional fields. Recently, some institutions have created separate tenure tracks for such positions, which may also be given other names such as “lecturer with security of employment”.
Other faculty who are not on the tenure track in the U.S. are often classified as Lecturers(or more advanced Senior Lecturers ) orInstructors, who may teach full-time or have some administrative duties, but have no research obligations (essentially the opposite of “research-only” faculty (or “research-only staff,” which has no true counterpart because teaching positions are almost always “faculty” – except for student-assistantships), which also come in various forms and may be either tenure-track or not. Both Lecturers and Instructors typically hold advanced graduate/professional degrees. The term “professor” as a common noun – as well as “Prof.” as a prenominal form of address – may be used for persons holding any kind of faculty position; however, the prenominal title of “Dr.” is reserved exclusively for those who have obtained doctoral degrees (typically a Ph.D., in academia, in contrast to the more common use of “Dr.” in the general public for physicians holding an MD/DO). In academic medicine, Instructor usually denotes someone who has completed residency, fellowship, or other post-doctoral (MD/DO) training but who is not tenure-track faculty.
Any faculty title preceded with the qualifier“Adjunct” theoretically denotes part-time status (usually less than half-time). Adjunct faculty may have primary employment elsewhere (either another school, or as a practicing professional), though in today’s saturated academic market many doctorate-holders seek to earn a living from several adjunct jobs (to the advantage of institutions, which do not typically offer such faculty retirement/health benefits or long-term contracts).