In constitutional usage in Commonwealth realms and in some other systems, a ministry (usually preceded by the definite article, i.e., the ministry) is a collective body of government ministers headed by a prime minister or premier, and also referred to as the head of government. It is described by the Oxford Dictionary as "a period of government under one prime minister". Although the term "cabinet" can in some circumstances be a synonym, a ministry can be a broader concept which might include office-holders who do not participate in cabinet meetings. Other titles can include "administration" (in the United States) or "government" (in common usage among most parliamentary systems) to describe similar collectives.
The term is primarily used to describe the successive governments of the United Kingdom, Canada, Australia and New Zealand, which share a common parliamentary political heritage. In the United Kingdom, Australia and New Zealand, a new ministry begins after each election, regardless of whether the prime minister is re-elected, and whether there may have been a minor rearrangement of the ministry. For example, after winning the 1979 general election, Margaret Thatcher (as Prime Minister of the United Kingdom) formed the first Thatcher ministry. After being re-elected at the 1983 general election, she formed the second Thatcher ministry, and so on. In Canada, a new ministry is only formed if the government loses an election or the succeeding prime minister being from the same party as his or her predecessor.
Despite the use of the term "ministry" in this sense being rare in Portugal nowadays, until the first half of the 20th century, the term was frequently used in this country to designate the collective body of government ministers. From 1911 to 1933, the official title of the Prime Minister of Portugal was even that of "President of the Ministry" (Portuguese: Presidente do Ministério), reflecting his role as the head of the collective ministry.