A beat is the basic time unit of a piece of music; for example, each tick sounded by a metronome would correspond to a beat. More technically, a beat is a pulse on the beat level, the metric level at which pulses are heard as the basic unit. Depending on the context, beat may denote either

• the onset of the corresponding time unit, a point in time, the very moment when the metronome ticks, or
• the complete time interval between two consecutive taps, so to say, or
• in popular music, the whole sequence of individual beats (in the sense of meter, rhythm, groove, or riddim).

Much music is characterised by a sequence of stressed and unstressed beats (often called "strong" and "weak") organised into a meter and partially indicated by a time signature, the speed of which is determined by a tempo. In the context of a time signature, the term "beat" most often refers to the bottom number — so in 3/4, most people would consider the beat to be the 4; that is, a quarter-note, or crotchet. Musicians typically find that mentally counting a regular series of beats enables them to keep synchronised even if the music is not characterised by regular rhythm.

Metric levels faster than the beat level are division levels, and slower levels are multiple levels.

A hyperbeat is one unit of hypermeter, generally a measure, as is to a hypermeasure what a beat is to a measure. (Stein 2005, p.329)

In hip hop music, the term 'beat' has come to be defined as the entire instrumental, non-vocal portion of the song.

Beat, also known as Merseybeat (for bands from Liverpool (in Merseyside)), Brumbeat (for bands from Birmingham) etc., is a pop music genre that evolved in the UK in the early 1960s. Beat groups characteristically had simple guitar-dominated line-ups, with vocal harmonies and catchy tunes. Beat music has little to do with the Beat Generation literary movement of the 1950s, and more to do with driving rhythms, which the bands had adopted from their R&B/soul influences.