De facto is a Latin expression that means "in fact" or "in practice", commonly used as opposed to de jure (meaning "by law") when referring to matters of law or governance or technique (such as standards), that are found in the common experience as created or developed without or against a regulation.

Table of contents
1 De facto standards
2 De facto rulers
3 Other usages

De facto standards

A de facto standard, for instance, is a technical or other standard that is so dominant that everybody seems to follow it like an authorized standard. The de jure standard may be different: one example is the metric unit of kilometre, which is the de jure standard for road distances in the United States, while the mile (=1609.344 m) is the de facto standard. In addition, there is no law preventing one from adding a twenty-seventh letter such as þ to the alphabet, as letters were added, centuries ago, without much difficulty, but one is prevented from doing so today by the practical difficulties involved. Thus there is a de facto limit on modifications to the alphabet. The de facto standard is not even formalized in all cases and may simply rely on the fact that someone has come up with a good (hopefully unpatented) idea that everybody else likes so much that it is copied/plagiarized. Typical creators of de facto-standards are individual companies, corporations and consortiums.

De facto rulers

In politics, one speaks of a de facto leader of a country or region, meaning one who has illegally assumed authority, typically by deposing a previous leader or undermining the rule of a current one. De facto leaders do not usually hold a constitutional office, and exercise power in an informal manner. It is important to note that not all dictators are de facto rulers. Many current and past dictators have initially emerged as de facto leaders, but later formalize their rule through constitutional revisions. For example, Augusto Pinochet of Chile initially came to power as the chairman of a military junta, but then later amended the nation's constitution and made himself president, thus making him the formal and legal ruler of Chile.

Some notable true de facto leaders have been Deng Xiaoping of the People's Republic of China and General Manuel Noriega of Panama. Both of these men exercised near total control over their respective nations for many years despite not having the legal authority to do so.

De facto has also been used in reference to the role the Governor-General of individual commonwealth countries plays as head of state. While they are constitutionally appointed by the Crown to serve as representative of the monarch, who is the de jure head of state, they actually function independently of the monarch and function as the day to day head of state in each otherwise independent former colony of the British Empire. They are usually selected by the Prime Minister of the country and since the 1970s have always been citizens of that country and not of any other member of the Commonwealth or the United Kingdom. Historically the office of Governor-General was an actual appointment by the Crown in Westminster and it had political significance during the British Empire.

Other usages

Another common usage of the term de facto is "de facto segregation": Users of a given library or school tend to be residents of that neighborhood, and thus such facilities tend to become racially or ethnically segregated without "de jure segregation" (which would require segregation by force of law).

A de facto monopoly or oligopoly is a system where multiple or infinite players are allowed, but there is too much deregulation (not existing antitrust laws in general or in the specific economic sector, specially in the utilities) or where antitrust law is not applied.

One's unmarried partner is referred to as the de facto husband or wife by some authorities. This has passed into the Australian language as the slang term defacto to refer to one's significant other. e.g. "This is my defacto, Rachael". In other territories, e.g. the UK, this is equivalent to the term common law husband or wife.

See also: List of Latin phrases