In the university setting in the U.S. and Canada, the three typical types of tenure track positions are assistant professor, associate professor, and professor. Tenure tracks can also be distinguished by external versus senior positions. Although educational systems in many other countries offer their faculty a type of permanent job contract, it is in North America that the specific phrasing of the position as tenure is traditionally applied.
Tenure is the extension of a permanent job offer to a faculty member, typically in the college or university setting. This type of job security is also awarded, particularly in some U.S. states, at different academic levels in some school systems, but the traditional use of this type of permanent employment is in the realm of higher education. The grant of tenure means that a professor cannot be fired by the university except under extraordinary circumstances typically involving unusual misconduct.
Teachers who work in a higher education setting are hired in either tenure track positions or non-tenure track positions. The distinguishing feature between the two types of employment is that a non-tenure track hire has no expectation of receiving an offer of permanent employment from the school. Non-tenure track teachers can remain employed by the school on a year-to-year, at-will basis into perpetuity but are not eligible for a permanent contract.
The most basic distinction in the types of tenure track positions is in the way a tenure eligible line is filled. When a college or university decides to add another tenured professor to an academic department, it either hires a recent PhD graduate and places him at the beginning of the tenure track pipeline or it hires a professor from another university that is either tenured or up for tenure. The second type of appointment is called a senior hire, and it places the new faculty member directly into a tenured position without having to wait the typical five years for tenure review.
External tenure-eligible faculty members are typically hired as assistant or associate professors. These two titles are the traditional tenure track positions that lead to a tenure review after approximately five years and the eventual designation as a fully tenured professor. There are many other faculty titles in use at colleges and universities, such as adjunct professor and lecturer, but the title progression that goes from assistant to associate to full professor is usually reserved as the tenure track designation.