A sacred language, holy language or liturgical language is any language that is cultivated and used primarily for religious reasons (like church service) by people who speak another, primary language in their daily lives.
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; these texts thereafter become fixed and holy, remaining frozen and immune to later linguistic developments. (An exception to this is Lucumí, a ritual lexicon of the Cuban strain of the Santería religion, with no standardized form.)
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 laypeople cannot (or should not) access.
Because sacred languages are ascribed with virtues that the vernacular is not seen to have, these typically preserve characteristics lost in the course of language development. In some cases, the sacred language is a dead language, while in others, 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 from 1611, 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 barely comprehensible without special training.