De jure
De jure (in Classical Latin de iure) is an expression that means "based on law", as contrasted with de facto, which means "in fact".
The terms de jure and de facto are used instead of "in principle" and "in practice", respectively, when one is describing political situations. They are also often used when discussing racial segregation. A practice may exist de facto, where the people obey a contract as though there were a law although there is none. A process known as "desuetude" may allow de facto practices to replace obsolete laws. On the other hand, practices may exist de jure and not be obeyed or observed by the people.
The Latin de jure should not be confused with the French du jour, which translates to "of the day", as, for example, in soupe du jour, or soup of the day.
De jure and de facto standards can differ; for example, the U.S. has no de jure language, whereas the de facto language is English. Similarly, the U.S. de jure standard for measurement of road distances is the kilometre (as the U.S. is party to the Convention du Mètre), but the de facto standard is the mile.
