The meaning of the word professor (Latin: professor, person who professes to be an expert in some art or science, teacher of highest rank) varies. In some English-speaking countries, it refers to a senior academic who holds a departmental chair, especially as head of the department, or a personal chair awarded specifically to that individual. For example, in the United Kingdom, Ireland, South Africa, Australia, New Zealand, United States, Canada, and Hong Kong it is a legal title conferred by a university denoting the highest academic rank. However, in some institutions, the term is used only for academics who are tenured or tenure-track. In some countries, e.g. Austria, Brazil, Democratic Republic of the Congo, France, Romania, Slovenia, Croatia, Serbia, Poland, Spain and Italy, the term is an honorific applied also to secondary level teachers.

Professors are qualified experts, of the various levels described above, who may do the following:

• conduct lectures and seminars in their field of study (i.e., they "profess"), such as the basic fields of science, humanities, social sciences, education, literature or the applied fields of engineering, design, music, medicine, law, or business;
• perform advanced research in their fields.
• provide pro bono community service, including consulting functions (such as advising government and nonprofit organizations);
• teach campus-based or online courses with the help of instructional technology;
• train young or new academics (graduate students);
• carry out administrative or managerial functions, usually at a high level (e.g. Deans, Heads of Department, librarians, etc.).

The balance of these six fields of professorial tasks depends heavily on the institution, place (country), and time. For example, professors at highly research-oriented universities in the U.S., and Canada, and, as a general rule, in European universities, are promoted primarily on the basis of their research achievements as well as their success in raising money from sources outside the university.

Tenure

A tenured professor has a lifetime appointment until retirement, except for dismissal with "due cause". The reason for the existence of such a privileged position is the principle of academic freedom, which holds that it is beneficial for state, society and academe in the long run if learned persons are free to examine, hold, and advance controversial views without fear of losing their jobs. Tenure allows professors to engage in current political or other controversies. Critics assert that it also means that lazy or unpleasant professors cannot be forced to improve, and have suggested including management techniques from the business world such as performance review, audits, and performance-based salaries. In many cases, individuals enter academia because they are intrinsically interested in the work, and so they are often very unlikely to use tenure as an excuse to withdraw from their research responsibilities. In fact, even in cases where there is mandatory retirement, many professors continue to be active researchers. However, tenured professors may be more prone to neglecting their teaching duties, if they lack interest in pedagogy.