A biquintile is the aspect of one hundred and forty-four degrees, two fifths of the circle. It is one of the minor aspects introduced by Johannes Kepler alongside the quintile, set out in the same passage of the Harmonices Mundi of 1619 and derived from the same argument, that consonant musical ratios, expressed geometrically through the regular polygons constructible by compass and straightedge, ought to determine which angles count as workable aspects.
One hundred and forty-four degrees is the interior angle of the regular pentagon, so the biquintile and the quintile belong to the same fivefold geometric family, the pentagon and the five-pointed pentagram, even though the two aspects are read somewhat differently: the biquintile is generally taken as the stronger or more concentrated expression of the pair, describing creative aptitude, a gift for form and design, and a facility that shows itself in the making of things rather than in ideas alone. Like the quintile it has no settled glyph of its own, and because both angles emerge from the same construction of the regular pentagon and decagon, some later harmonic astrologers have proposed a fuller family of related tenfold and fivefold divisions, among them the decile and tredecile, though only the quintile and biquintile from that wider set achieved anything like regular use.