An executive officer (often abbreviated XO) is generally a person responsible for running an organization, although the exact nature of the role varies depending on the organization.
While there is no clear line between executive or principal and inferior officers, principal officers are high-level officials in the executive branch of U.S. government such as department heads of independent agencies. In Humphrey's Executor v. United States, 295 U.S. 602 (1935), the Court distinguished between executive officers and quasi-legislative or quasi-judicial officers by stating that the latter serve at the pleasure of the president and may be removed at his discretion. The former are removed only with procedures consistent with statutory conditions enacted by Congress. The decision by the Court was that the Federal Trade Commission was a quasi-legislative body because of other powers it had, and therefore, the president could not fire an FTC member for political reasons. Congress can’t retain removal power over officials with executive function (Bowsher v. Synar). However, statutes can restrict removal if not purely executive (Humphrey’s executor), but can't restrict removal of purely executive officer (Myers v. United States, 272 U.S. 52 (1926)). The standard is whether restriction "impedes the president’s ability to perform his constitutional duty" (Morrison v. Olson, 487 U.S. 654 (1988)).
In business, the executive officers are the top officers of a corporation, the chief executive officer (CEO) being the best-known type. The definition varies; for instance, the California Corporate Disclosure Act defines "executive officers" as the five most highly compensated officers not also sitting on the board of directors. In many insurance policies, executive officer means, in the case of a corporation, any chairman, chief executive officer, chief financial officer, chief operating officer, president, or general counsel. In the case of a sole proprietorship, an executive officer is the sole proprietor. In the case of a partnership, an executive officer is a managing partner, senior partner, or administrative partner. In the case of a limited liability company, an executive officer is any member, manager, or officer.