De facto language

From Teflpedia

A de facto language (/də ˈfæktəʊ ˈlæŋ(g)wɪʤ/) is an individual language that is used for official purposes within a jurisdiction, but is not a de jure official language.

English is the de facto language of both the United Kingdom and the United States, rather than being an official language. In both cases, it is also the majority language.