Around parliamentary systems prefer a Westminster system, the prime minister is the head of the government while the position of head of state is largely ceremonial. Inside a select few monarchies a prime minister exercises powers (known as the Royal Prerogative) which are constitutionally vested in a Crown & may be exercised forswearing the approval of parliament. Too when existence Head of Government, a prime minister could keep around more roles or even titles—the Prime Minister of the United Kingdom, for instance, is as well First Lord of the Treasury. Prime ministers could choose more ministerial posts—e.g. in a period of the Second World War Winston Churchill was also Minister of Defence.

Prime ministers in republics and in monarchies
A post of prime minister is of these which can be found each inside constitutional monarchies (such as Belgium, Denmark, Japan, the Netherlands, Norway, Spain, and a United Kingdom), and around republics in which a head of state is an elective (like France) or unelected official (like Germany) with variable degrees of rattling power. This contrasts by having a presidential system, in which a President (or same) is each a head of state & a head of the government. Understand too "First Minister" , "Premier", "Chief Minister" "Chancellor and "Taoiseach": alternative titles usually equivalent in meaning to "prime minister."

In some presidential or semi-presidential systems such as those of France, Russia, South Korea, or Taiwan the prime minister is an official generally appointed by the President but approved by the legislature and responsible for carrying out the directives of the President and managing the civil service. In these systems, it is possible for the president and the prime minister to be from different political parties if the legislature is controlled by a party different from that of the president. When it arises, such a state of affairs is usually referred to as (political) cohabitation.

Entry into office

In parliamentary systems a prime minister can enter into office by a number of means.

by appointment by the head of state without the need for confirmation by parliament; Examples: New Zealand, the United Kingdom, where the monarch appoints a prime minister without the need for confirmation from parliament, which gets its first chance to indicate its view on the new government in the vote on the Speech from the Throne, in which the new government outlines its legislative programme. The method of prime ministerial appointment by the British sovereign is known as Kissing Hands. In Austria the chancellor takes office immediately after appointment and swear in by the Federal president. 'appointment by the head of state after parliament nominates a candidate; Example: The Republic of Ireland where the President of Ireland appoints the Taoiseach on the nomination of the Dáil Éireann.) appointment by the head of state after the majority parliamentary party nominates a candidate; Example: the Australian federal government, Canada, India, and New Zealand. the head of state nominates a candidate for prime minister who is then submitted to parliament for approval before appointment as prime minister; Example: Spain, where the King sends a nomination to parliament for approval. Also Germany where under the Basic Law (constitution) the Bundestag votes on a candidate nominated by the Federal President. In these cases, parliament can choose another candidate who then would be appointed by the head of state.) the head of state appoints a prime minister who has a set timescale within which s/he must gain a vote of confidence; (Example: Italy.) direct election by parliament (the premiers of the Northwest Territories and Nunavut); direct election by the public (Example: Israel, 1996-2001.); The Prime Minister is elected in a general election, with no regard to political affiliation. appointment by a state office holder other than the head of state or his/her representative;' Example: Under the modern Instrument of Government 1974, which came into force in 1975, the power of commissioning someone to form a government was moved from the Monarch of Sweden to the Speaker of Parliament, who, once it has been approved, formally makes the appointment.

''Though most prime ministers are 'appointed', they are generally, if inaccurately, described as 'elected'.

Prime ministers and constitutions

The position, power and status of prime ministers differ depending on the age of the constitution in individuals.

'Britain's' constitution, being uncodified and largely unwritten, makes no mention of a prime minister. Though it had de facto existed for centuries, its first official mention in official state documents did not occur until the first decade of the twentieth century.

'Australia's' Constitution makes no mention of a prime minister of Australia. The office has a de facto existence at the head of the Executive Council.

'Ireland's constitution, Bunreacht na hÉireann (1937) provided for the office of taoiseach in detail, listing powers, functions and duties.

Germany's' Basic Law (1949) lists the powers, functions and duties of the federal Chancellor.

Exit from office

Contrary to popular and journalistic myth, most prime ministers in parliamentary systems are not appointed for a specific term of 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 remained continuously'' in power until 1990, though she used the assembly of each House of Commons after a general election to reshuffle her cabinet. Some states, however, do have a term of office of the prime minister linked to the period in office on the parliament. Hence the Irish Taoiseach is formally 'renominated' after every general election. (Some constitutional experts have questioned whether this process is actually in keeping with the provisions of the Irish constitution, which appear to suggest a taoiseach should remain in office, without the requirement of a renomination, unless s/he has clearly lost the general election.) The position of Prime Minister is normally chosen from the political party that commands majority of seats in the lower house of parliament.

In parliamentary systems, governments are generally required to have the confidence of the lower house of parliament (though a small minority of parliaments, by giving a right to block Supply to upper houses, in effect make the cabinet responsible to both houses, though in reality upper houses, even when they have the power, rarely exercise it). Where they lose a vote of confidence, have a motion of no confidence passed against them, or where they lose Supply, most constitutional systems require either:

a) a resignation or

b) a request of a parliamentary dissolution.

The latter in effect allows the government to appeal the opposition of parliament to the electorate. However in many jurisdictions a head of state may refuse a parliamentary dissolution, requiring the resignation of the prime minister and his or her government. In most modern parliamentary systems, the Prime Minister is the person who decides when to request a parliamentary dissolution. Older constitutions often vest this power in the cabinet. (In Britain, for example, the tradition whereby it is the prime minister who requests a dissolution of parliament dates back to 1918. Prior to then, it was the entire government that made the request. Similarly, though the modern 1937 Irish constitution grants to the Taoiseach the right to make the request, the earlier 1922 Irish Free State Constitution vested the power in the Executive Council (the then name for the Irish cabinet).

Titles
A number of different terms are used to describe prime ministers. The German prime minister is actually titled Federal Chancellor while the Irish Prime Minister is called the Taoiseach. In many cases, though commonly used, "prime minister" is not the official title of the office-holder; the British prime minister is (usually) "Number 1 Lord of the Treasury & Minister for the Civil Service", and the Spanish prime minister is the President of the Government (Presidente del Gobierno). Other common forms include President of the Council of Ministers (for example in Italy, Presidente del Consiglio dei Ministri), President of the Executive Council, or Minister-President. In federations, the head of government of a state or province is most commonly known as the Premier or Chief Minister.

Style of a Prime Minister

The title Prime Minister is a job title that does not form part of the Prime Minister's name. It is therefore poor style to refer to “Prime Minister Blair”, just as it would be strange to call someone “Bus Driver Edwards”. The correct form is "Prime Minister Tony Blair" or "Tony Blair, Prime Minister". This mistake is particularly common in the United States, where a high office title is often adopted as if it were a military rank.

The title of Prime Minister is lost when the officer holder ceases to be Prime Minister. This is not the case for some comparable positions in the United States, which can cause some confusion. When former New Zealand Prime Minister Jim Bolger became the Ambassador to the United States, he was referred to as “Prime Minister Bolger”, which was both poor style and factually incorrect.

Commonwealth Realm Prime Ministers are often Privy Counsellors entitled to the style the right honourable. In the New Zealand Parliament's debating chamber the Prime Minister is referred to as the Right Honourable the Prime Minister, rather than by name.

In non-Commonwealth countries the Prime Minister may be entitled to the style of Excellency like a President.

Articles on prime ministers
Prime Minister of Australia Chancellor of Austria Chancellor of China Prime Minister of Belgium Prime Minister of Canada Prime Minister of France Prime Minister of Fiji Chancellor of Germany Prime Minister of India Prime Minister of Iran Taoiseach of Ireland Prime Minister of Israel Prime Minister of Japan Prime Minister of Malaysia Prime Minister of the Netherlands Prime Minister of Newfoundland (historical) Prime Minister of New Zealand Prime Minister of Norway Prime Minister of Pakistan Prime Minister of the Republic of Poland Prime Minister of Serbia Prime Minister of Slovenia President of the Government of Spain Prime Minister of Sweden Prime Minister of the United Kingdom

Lists of prime ministers
The following table groups the list of past and present prime ministers and details information available in those lists.