What is "niddah"

n. (context Judaism English) Someone whom halacha considers menstruant.

Niddah (or nidah; ) is a Hebrew term describing a woman during menstruation, or a woman who has menstruated, and not yet completed the associated requirement of immersion in a mikveh (ritual bath).

In Leviticus, the Torah prohibits sexual intercourse with a niddah and the prohibition has been maintained in traditional Jewish law. The laws concerning niddah are also referred to as taharath hamishpacha (טהרת המשפחה, Hebrew for family purity).