Nāmūs is the Arabic word (Greek "νόμος") of a concept of an ethical category, a virtue, in Middle Eastern patriarchal character. Literally translated as "virtue", it is now more popularly used in a strong gender-specific context of relations within a family described in terms of honor, attention, respect/respectability, and modesty.
The concept of namus in respect to sexual integrity of family members is an ancient, exclusively cultural concept which predates Islam, Judaism, and Christianity.
The Arabic word "nāmūs" (ناموس) may mean "law", "custom" or "honor". The Ancient Greek word "nómos" (νόμος) means "law, custom".
For a man and his family, namus may, on the one hand, mean sexual integrity of women in the immediate family, their chastity in particular. On the other hand, the man has to provide for his family and to defend the namus of his house, his women in particular, against the threats (physical and verbal) to members of his extended family from the outer world.
Namus of a man is determined by namus of all the women in his family (i.e., mother, wives, sisters, daughters). In some societies, e.g., in Pashtun tribes of Afghanistan, namus goes beyond the basic family and is common for a plarina, a unit of the tribe that has a common ancestral father.
For an unmarried woman, the utmost importance is placed on virginity before marriage. There is a requirement in some cultures for "proof of virginity" (in the form of bloodstains on a bed sheet) to be proudly displayed after the wedding night. Professor of sociology Dilek Cindoğlu writes: "The virginity of the women is not a personal matter, but a social phenomenon".