High Gothic
High Gothic is the hieratic tongue of the Imperium of Man, used in the formal titles of Imperial organizations (such as the Adeptus Terra, Adeptus Astartes, Astra Militarum). It is an older language than the commonly used Imperial vernacular and is regarded as a sacred tongue since it was the language spoken by the Emperor of Mankind himself.
High Gothic first developed during the Dark Age of Technology on Old Earth before the spread of Mankind to its interstellar colonies. It derives from the common tongue of that time; an assimilation of English, European and Asian-Pacific languages which developed over many centuries. High Gothic was the universal medium of Humanity's written record in the late Age of Terra and the Age of Technology until the advent of the Age of Strife, and was spoken as a first language by many and as a second language by almost everyone.
Its idioms and vocabulary now appear archaic and mystic to the peoples of the present-day Imperium and many of its words have acquired religious significance over the years. It is unintelligible to most Imperial citizens; it is the language of important Adepts and only a second language even among them. It is used principally in formal situations (such as during pious benedictions by a priest of the Ecclesiarchy), rather than as a casual language of conversation.
Low Gothic or Gothic, a bastardised, present-day version of High Gothic, is the current common tongue of the Imperium in the late 41st Millennium.