[f., pl. “Niddot”]; literally “removed or separated;” generally in the context of Jewish Marital Laws (known as “Taharat HaMishpacha,” or Family Purity). When a married woman is in the menstrual state, Jewish Law requires a period of separation from her husband.
It is the obligation of the woman to examine herself, and if she detects even the smallest drop of blood, she must inform her husband, and they must withdraw from each other, until her period of “clean days” is over. Then she should immerse herself in a Mikvah, and afterwards, they should return to each other and resume normal marital relations.
Prophets also use the term to depict the People of Israel when they are involved in sin, such as immorality or idol-worship or violence, and consequent estrangement from HaShem.