Book excerpt: Menstruation across Cultures attempts to provide a detailed review of menstruation notions prevalent in India and in cultures from across the world. The world cultures covered in the book include Indic traditions like Hinduism, Buddhism, Jainism and Sikhism; ancient civilisations like Greece, Rome, Mesopotamia and Egypt; and Abrahamic religions of Judaism, Christianity, and Islam. Two themes of special focus in the book are: Impurity and Sacrality. While they are often understood as being opposed to each other, the book examines how they are treated as two sides of the same coin, when it comes to menstruation. This is especially true in Indic traditions and pre-Christian polytheistic traditions like Greco-Roman, Mesopotamian and Egyptian. Impurity and Sacrality complement each other to form a comprehensive worldview in these cultures. The book also examines how the understanding of impurity in Abrahamic religions differs from those of polytheistic cultures. As part of the examination of the sacrality attached to menstruation, a special focus has also been given to the deities of menstruation in polytheistic cultures and to what Ayurveda and Yoga say about this essential function in a woman’s physiology. Finally, a comparative study of menstrual notions prevalent in modernity is presented, along with a Do and Don’t dossier.