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Emeritus ( //; female: Emerita), [Note 1] in its current usage, is an adjective used to designate a retired chair, professor, pastor, bishop, pope, director, president, prime minister, rabbi, emperor, or other person who has been "permitted to retain as an honorary title the rank of the last office held". 
In some cases, the term is conferred automatically upon all persons who retire at a given rank, but in others, it remains a mark of distinguished service, awarded only to a few on retirement. It is also used when a person of distinction in a profession retires or hands over the position, enabling their former rank to be retained in their title, e.g., "professor emeritus". The term emeritus does not necessarily signify that a person has relinquished all the duties of their former position, and they may continue to exercise some of them.
Emeritus (past participle of Latin emerere, meaning "complete one's service") is a compound of the Latin prefix e- (variant of ex-) meaning "out of, from" and merere (source of "merit") meaning "to serve, earn". The word is attested since the early 17th century with the meaning "having served out one's time, having done sufficient service." The Latin feminine equivalent, emerita ( //), is also sometimes used, however, in English the word emeritus is often unmarked for gender. 
In the United States and other countries, a tenured full professor who retires from an educational institution in good standing may be given the title "professor emeritus". The title "professor emerita" is sometimes used for women. In most systems and institutions, the rank is bestowed on all professors who have retired in good standing, while at others, it needs a special act or vote. Professors emeriti may, depending on local circumstances, retain office space or other privileges. The adjective may be placed before or after the title, e.g., "professor emeritus" or "emeritus professor". Emeritus is sometimes applied to tenured associate professors or non-tenure-track faculty.
In the United Kingdom and most other parts of the world, the term "emeritus professor" is given only to a person of outstanding merit who had full professorial status before he or she retired. The possession of a PhD or other higher degree, or even full professorial status, is not sufficient for calling oneself "emeritus professor" upon retirement. The term "Professor Emeritus" is also recognised in the United Kingdom. The word is capitalized when it forms part of a title which is capitalized.
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When a diocesan bishop or auxiliary bishop retires, the word emeritus is added to his former title, i.e., "Archbishop Emeritus of ...". The term "Bishop Emeritus" of a particular see can apply to several people, if the first lives long enough. The title was applied to the Bishop of Rome, Pope Emeritus Benedict XVI, on his retirement. In Community of Christ, the status of emeritus is occasionally granted to senior officials upon retirement. In Judaism, emeritus is often a title granted to long-serving rabbis of synagogues or other Jewish institutions. In some cases, the title is also granted to chazzans. Rabbi Emeritus or Cantor Emeritus is largely an honorific title.
Since 2001, the honorary title of president pro tempore emeritus has been given to a senator of the minority party who has previously served as president pro tempore of the United States Senate. The position has been held by Strom Thurmond (R-South Carolina) (2001–2003), Robert Byrd (D-West Virginia) (2003–2007), Ted Stevens (R-Alaska) (2007–2009), Patrick Leahy (D-Vermont) (2015–2021) and Chuck Grassley (R-Iowa) (beginning in 2021).
It is also used in business and nonprofit organizations to denote perpetual status of the founder of an organization or individuals who made significant contributions to the institution.
- President pro tempore emeritus of the United States Senate
- Daijō Tennō (retired Emperors of Japan)
- Diocesan bishop (bishop emeritus in the Catholic Church)
- Pope Emeritus
- List of academic ranks
- feminine emerita or emeritus; plural emeriti (masc.) or emeritae (fem.); abbreviation emer.
- Emeritus, New Oxford American Dictionary (2nd edition), 2005.
- Emeritus, Australian Concise Oxford Dictionary (3rd edition), 1997.