Under the doctrine of the separation of powers, the executive is the branch of a government charged with implementing, or executing, the law and running the day-to-day affairs of the government or state. The de facto most senior figure in an executive is referred to as the head of government. The executive may be referred to as the administration, in presidential systems, or simply as the government, in parliamentary systems.

In some constitutional monarchies, such as the United Kingdom, the monarch, who is the Head of State, is the de jure and theoretical head of the executive, and the Prime Minister, who he or she technically appoints, is the head of the monarch's government (i.e. "Her Majesty's Government"). In practice, however, a symbolic or figurehead Head of State does not actively exercise executive power, though decisions may be formally made in his or her name.

Along with the Prime Minister or executive President, the executive branch consists of the cabinet and the executive departments or ministries of the government.

Executives under different systems

Executive authority within a presidential system is exercised by a president who is also head of state. The president will not usually be designated by the legislature, and may instead be elected directly, or in the case of the President of the United States, indirectly, by an electoral college. Under presidential systems the legislature and the executive are formally distinct, and it is usually expressly forbidden for the president and other executive officers to be members of the legislature.

In parliamentary systems, the executive branch is generally comprised of a prime minister and a cabinet, who must directly or indirectly secure the support of the legislature.

In a semi-presidential system (such as France, for example) executive powers are shared between the president and a prime minister.

Role of the executive

It is usually the role of the executive to:

• Enforce the law. To achieve this the executive administers the prisons and the police force, and prosecutes criminals in the name of the state.
• Conduct the foreign relations of the state.
• Command the armed forces.
• Appoint state officials, including judges and diplomats.
• Administer government departments and public services.
• Issue executive orders (also known as secondary legislation, ordinances, edicts or decrees).

Most constitutions require that certain executive powers may only be exercised in conjunction with the legislature. For example, often the consent of the legislature is required to ratify treaties, appoint important officials, or to declare war. In the United Kingdom, however, the executive is exempt from most such limitations under the royal prerogative.