The Nunc dimittis is a canticle which is sung by some Christian sects during evening services. A canticle is a hymn which is taken directly from the Bible; in the case of the Nunc dimittis, the canticle is from the Gospel of Saint Luke. Many musicians have set this canticle to music, creating a variety of moods and versions, and it is generally taken to be a song of rejoicing and an affirmation of faith.
The section of the Bible which the Nunc dimittis comes from documents the presentation of the infant Jesus in Jerusalem. A devout Jew named Simeon has been told by God that he would not die until he saw the Saviour; the canticle puts the words of Simeon upon seeing the infant Jesus to song. It begins with the phrase Nunc dimittis, servum tuum, “now you have dismissed your servant,” and continues with words of praise and joy.
As you can see, the name of this canticle is taken from the first two words of its Latin version. It can also, of course, be sung in English or other languages. The Nunc dimittis is a celebration of salvation, and it often appears in Anglican churches, sung to a variety of compositions. Some of the most elegant compositions are plainchant versions from the medieval period.
You may also hear the Nunc dimittis referred to as the Song or Canticle of Simeon, a reference to its leading character. This particular canticle is extremely well known, and it is often referenced in works by Western authors who assume that people are familiar with the form of the Nunc dimittis.
As you might imagine, there are a number of different translations of the Nunc dimittis into English. In the King James Bible, a widely used translation, it reads in full: “Lord, now lettest thou thy servant depart in peace, according to thy word: For mine eyes have seen thy salvation, Which thou has prepared before the face of all people; A light to lighten the Gentiles, and the glory of thy people Israel.”