עֵד‎ (ʻêd|ayd|noun|feminine|menstruation)
[Heb] עֵד‎, עִדָּה‎ ETCBC: עִדָּה‎ (subs|menstruation) OSHL: p.ap.ab TWOT: 1564a GK: H6340
Derivation: from an unused root meaning to set a period (compare עָדָה‎, עוּד‎);
Strong's: the menstrual flux (as periodical); by implication (in plural) soiling
KJV: filthy.