A hymn is a type of song, and partially synonymous with devotional song, specifically written for the purpose of adoration or prayer, and typically addressed to a deity or deities, or to a prominent figure or personification. The word hymn derives from Greek ὕμνος (hymnos), which means "a song of praise". A writer of hymns is known as a hymnist. The singing or composition of hymns is called hymnody. Collections of hymns are known as hymnals or hymn books. Hymns may or may not include instrumental accompaniment. Polyhymnia is the Greco/Roman goddess of hymns.

A song is a musical composition performed by the human voice. The voice often carries the melody using patterns of sound and silence. Songs have a structure to them, such as the common ABA form, and are usually made of sections that are repeated or performed with variation later. A song without instruments is said to be a cappella.