Emeritus ( /ɨˈmɛrɨtəs/; plural emeriti; abbreviation emer.) is a post-positive adjective that is used to designate a retired professor, bishop, or other professional or as a title. The female equivalent emerita (/ɨˈmɛrɨtə/) is also sometimes used, but phrases such as professor emerita are not proper usage according to Latin grammar.
In many cases the term is conferred automatically upon all persons who retire at a given rank. This is the usual case for retired professors. In other cases it is used when a person of importance in a given profession retires and/or hands over the position, so that his former rank can still be used in his title.
In the United States, the word is used either as a postpositional adjective (e.g., "professor emeritus"), or as a preposition adjective (e.g., "emeritus professor"). There is a third, somewhat less common usage, following the full title (e.g., professor of medicine, emeritus.)
It is also commonly used in business and non-profit organizations to denote perpetual status of the founder of an organization, or key individuals who moved the organization to new heights as a former key member on the Board of Directors (i.e. Chairman Emeritus; Director Emeritus; President of the Board Emeritus.)
In the United Kingdom and most other parts of the world, the term 'Emeritus Professor' is given only to people who already had full professorial status before they retired. Those with PhDs or other higher degrees would not be entitled to call themselves an 'Emeritus Professor' upon retirement. The term "Professor Emeritus" is also recognised in the UK but is generally only used by new universites; older more prestigious Russell Group universities favour the term "Emeritus Professor". The word is capitalised when it forms part of a title which is capitalised.
The word originated in the mid-18th century from Latin as the past participle of emereri meaning to "earn one's discharge by service." Emereri itself is a compound of the prefix e- (a variant of ex-) meaning "out of or from" and merēre meaning "earn." Emeritus does not necessarily indicate that the person is retired from all the duties of her/his previous positions; he/she may continue to exercise some of them.