A canticle is a hymn (strictly excluding the Psalms) taken from the Bible. The term is often expanded to included ancient non-Biblical hymns such as the Te Deum and certain psalms used liturgically. Its meaning can be further expanded to include:

• A song, especially a hymn (as in "Canticle of Canticles", another way to refer to the biblical book Song of Solomon.)
• A canto or division of a poem

Examples of Biblical canticles:

• Benedicite or Song of the Three Holy Children (Daniel III, 57–88 in the Apocrypha)
• Benedictus or Canticle of Zechariah (Luke I, 68–79)
• Magnificat or Song of the Blessed Virgin Mary (Luke I 46-55)
• Nunc dimittis

From the Latin "canticulum", a diminutive of "canticum", song.