Anacrusis

In poetic and musical meter, and by analogy in publishing, an anacrusis (from Greek: ἀνάκρουσις, anákrousis, literally: 'pushing up', plural anacruses) is a brief introduction. In music, it is also known as a pickup beat, or fractional pick-up, i.e. a note or sequence of notes, a motif, which precedes the first downbeat in a bar in a musical phrase.

It is a set of syllables or notes, or a single syllable or note, which precedes what is considered the first foot of a poetic line (or the first syllable of the first foot) in poetry and the first beat (or the first beat of the first measure) in music that is not its own phrase, section, or line and is not considered part of the line, phrase, or section which came before, if any.