A sacred language, "holy language" (in religious context) or liturgical language is a language that is cultivated for religious reasons by people who speak another language in their daily life.
A sacred language is often the language which was spoken (and written) in the society in which a religion's sacred texts were first set down; however, thereafter these texts, becoming fixed and holy, remain frozen and immune to later linguistic developments. Once a language becomes associated with religious worship, its believers may ascribe virtues to the language of worship that they would not give to their native tongues. In the case of sacred texts, there is a fear of losing authenticity and accuracy by a translation or re-translation, and difficulties in achieving acceptance for a new version of a text. A sacred language is typically vested with a solemnity and dignity that the vernacular lacks. Consequently, the training of clergy in the use of a sacred language becomes an important cultural investment, and their use of the tongue is perceived to give them access to a body of knowledge that untrained lay people cannot (or should not) access. In medieval Europe, the (real or putative) ability to read (see also benefit of clergy) scripture—which was in Latin—was considered a prerogative of the priesthood, and a benchmark of literacy; until near the end of the period almost all who could read and write could do so in Latin.
Because sacred languages are ascribed with virtues that the vernacular is not perceived to have, the sacred languages typically preserve characteristics that would have been lost in the course of language development. In some cases, the sacred language is a dead language. In other cases, it may simply reflect archaic forms of a living language. For instance, 17th-century elements of the English language remain current in Protestant Christian worship through the use of the King James Bible or older versions of the Anglican Book of Common Prayer. In more extreme cases, the language has changed so much from the language of the sacred texts that the liturgy is no longer comprehensible without special training.