Niddah is a term in Jewish law that refers to a woman during her menstrual period and for a certain time afterward. During this period, she is considered ritually impure and must refrain from physical intimacy with her husband. The laws surrounding Niddah are derived from the Torah and are observed by many Jewish communities. After the menstrual cycle ends, a woman must count seven clean days before she can immerse herself in a ritual bath, known as a mikvah. This immersion restores her status of ritual purity, allowing her to resume intimate relations with her husband.