Following the key signature is the time signature. The time signature typically consists of two numbers, with one of the most common being . The top "4" indicates that there are four beats per measure (also called bar). The bottom "4" indicates that each of those beats are quarter notes. Measures divide the piece into groups of beats, and the time signatures specify those groupings. is used so often that it is also called "common time", and it may be indicated with rather than numbers. Other common time signatures are (three beats per bar, with each beat being a quarter note); (two beats per bar, with each beat being a quarter note); (six beats per bar, with each beat being an eighth note) and (twelve beats per bar, with each beat being an eighth note; in practice, the eighth notes are typically put into four groups of three eighth notes. is a compound time type of time signature). Many other time signatures exist, such as , , , , , and so on.