Meter refers to the repetitive arrangement of strong and weak pulses in a musical composition. It comes from the Greek word for "measure" and is notated with a time signature at the beginning. The time signature indicates how many beats are in each measure and which note value (quarter note, half note, etc.) receives one beat. There are three main types of meter: duple meter groups beats in twos, triple meter groups beats in threes, and quadruple meter groups beats in fours. The time signature, along with the grouping of beats, establishes the underlying pulse or rhythm of a piece of music.