A Prime Minister is the leader of a government in a parliamentary system. The office is usually held by the head of the largest political party or, when there are multiple parties with equal numbers, the party that holds the most seats in parliament. A prime minister is responsible for setting government policy and appointing cabinet officials. In addition, they make major speeches to Parliament on government issues and are the person most frequently asked questions by members of the opposition during Question Time. Prime Ministers also take a prominent role in international politics, representing their country at summits and meetings of the heads of governments of member states of the Commonwealth of Nations.
In Britain, the title of the position is “First Lord of the Treasury” and the official residence is 10 Downing Street. In other countries the title may be called something else, and in some cases there is no formal name at all; instead, the powers of the position are defined by a complex set of uncodified rules, precedents, informal influences, and formal legislation.
In most countries, the prime minister is chosen by the head of state on a nomination from parliament. In some countries, a prime minister is elected directly by the legislature: for example, in Ireland, where the president appoints the Taoiseach on the nomination of Dail Eireann, or in the Philippines under its 1973 Constitution as amended under martial law. In addition, many of the powers and duties of the prime minister are formally defined in statute as being part of the royal prerogatives and therefore still vested in the sovereign, who remains head of state.