authority

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The power to enforce laws, exact obedience, command, determine, or judge.
• noun One that is invested with this power, especially a government or body of government officials.
• noun Power assigned to another; authorization.
• noun A public agency or corporation with administrative powers in a specified field.
• noun An accepted source of expert information or advice.
• noun A quotation or citation from such a source.
• noun Justification; grounds.
• noun A conclusive statement or decision that may be taken as a guide or precedent.
• noun Power to influence or persuade resulting from knowledge or experience.
• noun Confidence derived from experience or practice; firm self-assurance.

from The Century Dictionary.

• noun Power or admitted right to command or to act, whether original or delegated: as, the authority of a prince over subjects and of parents over children; the authority of an agent to act for his principal.
• noun The power derived from opinion, respect, or long-established reputation; influence conferred by character, office, station, mental superiority, or the like; credit: as, the authority of age or example; the authority of Aristotle.
• noun Power in a general sense.
• noun A person or persons, or a body, exercising power or command: generally in the plural: as, the civil and military authorities. The outward marks of authority; especially, the expression of authority in the countenance.
• noun That to which or one to whom an appeal or reference may be made in support of any opinion, action, or course of conduct.
• noun Weight of testimony; credibility: as, a historian of no authority; “authority of the Scriptures,”
• noun One who possesses adequate knowledge of a subject, and whose opinions or statements may be relied on; an expert; a standard author or his writings: as, an authority in matters pertaining to geology.
• noun In law, a precedent; a judicial decision; an official declaration or opinion, such as ought to be followed in similar cases.
• noun Justification; countenance; warrant.
• noun Synonyms Rule, dominion, government; warrant, permission, authorization.
• noun Influence, Authority, Ascendancy, Control, Sway, Domination, may all apply to persons or things, but seem primarily to belong to persons. Influence and authority imply moral power; the others may do so, and are considered to do so here. The words are arranged in the order of their strength. Influence may be small; it is wholly apart from the power of office; the word expresses the extent to which one affects the conduct or character of others simply by their deference to him on account of his station, wealth, ability, character, etc. Authority is, in this connection, influence amounting to a recognized right to command: as, the authority of age, wisdom, experience. It is presumably rightful, while the other words often express undue or unwholesome weight or power. Ascendancy is overmastering influence, supremacy by influence; the word is often used in a bad sense: as, the ascendancy of cunning over simplicity. Control is complete or successful and continued authority: as, his control over the convicts was maintained without resort to force. Sway is, by its derivation, control over that which may be viewed as a weighty or massive object; hence, a solid or powerful or controlling influence. Domination, as it may be an absolute and tyrannical rule, may also be an absolute and tyrannical influence or ascendancy: as, he was really under the domination of those whom he thought his servants or tools.

from the GNU version of the Collaborative International Dictionary of English.

• noun Legal or rightful power; a right to command or to act; power exercised buy a person in virtue of his office or trust; dominion; jurisdiction; authorization
• noun Chiefly in the plural. Government; the persons or the body exercising power or command
• noun The power derived from opinion, respect, or esteem; influence of character, office, or station, or mental or moral superiority, and the like; claim to be believed or obeyed
• noun That which, or one who, is claimed or appealed to in support of opinions, actions, measures, etc.
• noun Testimony; witness.
• noun A precedent; a decision of a court, an official declaration, or an opinion, saying, or statement worthy to be taken as a precedent.
• noun A book containing such a statement or opinion, or the author of the book.
• noun Justification; warrant.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun uncountable The power to enforce rules or give orders.
• noun used in singular or plural form Persons in command; specifically, government.
• noun countable A person accepted as a source of reliable information on a subject.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun freedom from doubt; belief in yourself and your abilities
• noun an authoritative written work
• noun official permission or approval
• noun an administrative unit of government
• noun the power or right to give orders or make decisions
• noun an expert whose views are taken as definitive
• noun (usually plural) persons who exercise (administrative) control over others