Polygonia comma Polygonia comma Polygonia comma, the eastern comma, is a North American butterfly in the family Nymphalidae, subfamily Nymphalinae. This butterfly is seasonally variable. The upperside of the summer form's hindwings are all black, whereas the winter forms hindwings are reddish orange. The underside of both forms is striped with dark and light brown. There is a silvery comma mark in the middle of the hindwing in both forms. Its wingspan is . The eastern comma may be spotted in woods near rivers, ponds, marshes, swamps, and other water sources. This butterfly seldom visits flowers, but rather feeds on sap, rotting
Pythagorean comma Pythagorean comma In musical tuning, the Pythagorean comma (or ditonic comma), named after the ancient mathematician and philosopher Pythagoras, is the small interval (or comma) existing in Pythagorean tuning between two enharmonically equivalent notes such as C and B (), or D and C. It is equal to the frequency ratio (1.5)/128 = about 1.01364, or about 23.46 cents, roughly a quarter of a semitone (in between 75:74 and 74:73). The comma which musical temperaments often refer to tempering is the Pythagorean comma. The Pythagorean comma can be also defined as the difference between a Pythagorean apotome and a Pythagorean