When constructing scales, a pair of notes related by diapason are considered to be equivalent. This relation is called octave equivalency, they are the same note, but on a different octave. This allows thinking of frequencies as wrapping around in a circle. The circle starts at unison and ends at diapason, except that unison and diapason are joined together to form the circle. Any frequency f which is smaller than 1 (unison) or larger than 2 (diapason) has an equivalent frequency within this circle: