Niddah – Niddah (or nidah; Hebrew: נִדָּה‎) 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).

Niddah – Wikipedia

https://en.wikipedia.org/wiki/Niddah

Niddah (or nidah; Hebrew: נִדָּה‎) 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).