An Etymological Dictionary of Astronomy and Astrophysics

A quantity that does not change during a particular process.

Etymology (EN): L. constantem “standing firm, stable,” pr.p. of constare, from → com- “together” + stare “to stand;”
PIE base *sta- “to stand;” cf. O.Pers./Av. sta- “to stand, stand still; set,” Pers. istâdan “to stand,”
Skt. sthâ- “to stand,” Gk. histemi “put, place, weigh,” stasis “a standing still,”

Etymology (PE): pâyâ verbal adj./noun from pâyidan “to stand firm, to be constant, steady, fixed,” Mid.Pers. pâyitan, pâtan, pây- “to protect; wait, stand,” Sogdian p’y “to protect, watch over,” O.Pers./Av. pâ(y)- “to protect, keep” pâtar- “protector, watcher,” cf. Skt. pâ- “to protect, keep,” pâti “protects,” Gk. poimen “shepherd,” poma “lid, cover,” L. pastor “shepherd,” panis “bread;” PIE base *pa- “to protect, guard, pasture, feed.”