lecturers' ranking in UK

just some general informaiton about promotion of staff in academia. In UK, the hierarchy of university lecturers is as follows:

1. temporary lecturer
2. Tenure track lecturer
3. junior lecturer
4. senior lecturer
5. reader
6. professor

temporary lecturer is someone who has a short contract for example for one year, tenure track is a longer contract say for example for 4-5 years. but when it comes to permanent lecturship, it is devided to junior and senior, then they are promoted to reader and finally professor. professors might get some extra honorary titles like School professor, or Professor in Law and so on. the reason why they use the title "reader" is not because they read the material to students, its story goes back to around 11th centure when Oxford university and generally universities were established in the Britain. There were not so many books at the time and lecturers apparently didn't have access to books, but readers had (or something like this stroy, i don't remember exactly).

In the USA, the system is different, they have:

1. instructor or teacher
   
2. assistant professor
3. associate professor
4. (full) professor

there are some other kinds of professors such as professor emeritus (a retired professor) and visitor professor (its meaning is self-evident).