Official language
An official language is a language that is given a unique legal status in the countries, states, and other territories. It is typically the language used in a nation's legislative bodies, though the law in many nations requires that government documents be produced in other languages as well.
Official languages are sometimes not the same as the medium of instruction and so, the two are not interchangeable.
Officially recognised minority languages
Officially recognised minority languages are often mistaken for official languages. However, a language officially recognised by a state, taught in schools, and used in official communication is not necessarily an official language. For example, Ladin and Sardinian in Italy and Mirandese in Portugal are only officially recognised minority languages, not official languages in the strict sense.
Political issues
In some countries, the issue of which language is to be used in what context is a major political issue; see List of issues in language and politics.