Prime minister leader, the incoming leader will usually be referred as "prime minister-in-waiting". An example or this situation was in 2016 in the United Kingdom when Theresa May was elected leader of the Conservative Party while David Cameron was still prime minister. Ukraine's constitution (1996) lists the powers, functions and duties of the Prime Minister of Ukraine. Most prime ministers in parliamentary systems are not appointed for a specific term in office and in effect may remain in power through a number of elections and parliaments. For example, Margaret Thatcher was only ever appointed prime minister on "one" occasion, in 1979. She
Acting prime minister Minister on 16 separate occasions. The term "acting Prime Minister" is sometimes also applied to someone who is temporarily appointed Prime Minister following a death in office (more commonly called a "caretaker Prime Minister" or an "interim Prime Minister"). Examples include Frank Forde (seven days following John Curtin's death), Earle Page (19 days following Joseph Lyons' death), and John McEwen (22 days following Harold Holt's disappearance). Unlike those who merely acted in the absence of a Prime Minister, Forde, Lyons, Page and McEwen were officially commissioned by the Governor General and took the oath of office; they are considered Prime