答曰．夫女子十四天癸至．腎氣全盛．沖流任通．血漸盈．應(yīng)時(shí)而下．常以三旬一見．愆期者病．故謂之經(jīng)候．然經(jīng)者．常也．候者．謂候一身之陰陽也．經(jīng)常之氣．伺候而至．若潮候之應(yīng)乎時(shí)也．天真之氣．與之流通．故一月一次行．平和則不失乎期．所以謂之經(jīng)候．又名月水也．