Reign

A reign is the period of a person's or dynasty's occupation of the office of monarch of a nation (e.g., Saudi Arabia, Belgium, Andorra), of a people (e.g., the Franks, the Zulus) or of a spiritual community (e.g., Catholicism, Tibetan Buddhism, Nizari Ismailism).^[1] In most hereditary monarchies and some elective monarchies (e.g., Holy Roman Empire) there have been no limits on the duration of a sovereign's reign or incumbency, nor is there a term of office. Thus, a reign usually lasts until the monarch dies, unless the monarchy itself is abolished or the monarch abdicates or is deposed.

In elective monarchies, there may be a fixed period of time for the duration of the monarch's tenure in office (e.g., Malaysia).

The term of a reign can be indicated with the abbreviation "r." (for Latin regnavit/rexit) after a sovereign's name,^[2] such as the following:

End of reign

A reign can be ended in several ways:

Emperor Ferdinand I of Austria, King of Hungary and Bohemia, King of Lombardy-Venetia (r. 1835–1848) was abdicated due to his disabilities (feeble-mindedness and epilepsy). His successor, Emperor Franz Josef (r. 1848–1916) reigned for 68 years.
King Edward VIII of the United Kingdom reigned from January to December 1936 before he abdicated the throne. After his abdication he became known as the Duke of Windsor. No other monarch of the Kingdom of Great Britain (1707–1800), the United Kingdom of Great Britain and Ireland, the United Kingdom of Great Britain and Northern Ireland, or any Dominion or Commonwealth realm has ever abdicated, though forced abdications did occur on rare occasions in the Kingdom of England and the Kingdom of Scotland prior to their merger in 1707.
Queen Wilhelmina of the Netherlands reigned from 1890 to 1948, before abdicating in favor of her daughter, Queen Juliana who then reigned until 1980 when she abdicated in favor of her daughter, Queen Beatrix of the Netherlands. Beatrix followed suit and abdicated in 2013 in favor of her son and heir apparent, King Willem-Alexander.

King Louis XVI of France reigned from 1774 until the overthrow of the monarchy in 1792 and his execution the following year.
Xuantong Emperor of China abdicated in 1912 following the Xinhai Revolution, marking the end of the Chinese monarchy.
King Umberto II of Italy reigned for only a few weeks in 1946 before the abolition of the Italian Monarchy.
King Constantine II of Greece reigned from 1964 until the abolition of the Greek monarchy in 1973.
Tsar Nicholas II of Russia reigned from 1894 until 1917 when he was forced to abdicate and the Russian Empire was overthrown during the Russian Revolution.
Emperor Haile Selassie of Ethiopia reigned for over 40 years (1930-1974) until the Derg forced him to abdicate and abolished the 3,000 year old monarchy, making him the 225th and final Emperor of Ethiopia.
Shah Mohammad Reza Pahlavi of Iran reigned for more than 37 years (1941–1979) until the Iranian Revolution, which superseded the 2,500 years of monarchy with an Islamic republic system of government. The Shah died the following year and is buried in Cairo.