以美国为例，教授评级次序依次为Assistant professor，Associate professor，Professor 或 full Professor，最后才是你所说的Distinguished professor / endowed chair。

一般来讲，
Assistant professor: An introductory level professor. A position generally taken after receiving PhD and/or completing a post-doctoral fellowship. After 4–8 years, assistant professors will be either tenured or dismissed from the university.
Associate professor: A mid-level, usually tenured, professor.
Professor (sometimes referred to as "full professor"): a senior, tenured professor.
Distinguished professor / endowed chair (e.g., "the John Q. Smith Professor of Physics"): An honorary position in which a full professor's salary is increased by being tied to an endowment derived from the university, private individuals, firms, or foundations.
助理教授是起点，拿到PhD学位和或完成博士后研究都可成为助理教授。比助理教授高点，我们在国内称副教授，现在国内副教授，教授数量较多，但是在美国一旦你评上副教授基本上是终身聘用了（据我所知哈佛系统是这样的）。副教授再次被擢升即为教授，一般科室的大主任级别较下属高，常为正教授或而该科室下属的小部门头目为副教授。荣誉XXX教授就是根据所在大学不同按情况授予，简单来讲就是教授里面比较牛的！
举例：美国哈佛医学院麻生总院麻醉科主任很牛，所以她的简历上出现的就是
Jeanine Wiener-Kronish, MD
Anesthetist-in-Chief; Henry Isaiah Dorr Professor of Anesthesia, Harvard Medical School （Henry Isaiah Dorr该称谓就表示她做出杰出成就及贡献，意思等同于 Distinguished professor / endowed chair ）