First: Purity in language: the source of the word طَهُرَ (tahara) means that something has become pure, and طَهُرَ is the opposite of نَجِس (najis). The noun is الطُّهْرُ (al-tuhru), which means being free from impurity and filth. It is also used to describe something that is pure in essence: that is, free from defect. Hence, the state that is contrary to menstruation is called طُهْر (tuhur). See: Al-Maghrib p. 295, and Al-Misbah Al-Munir p. 379. Second: Purity in Sharia: it is the cleanliness from minor or major impurities. Purity has two types: purity from minor impurities (حكمية طهارة - hukmiyyah taharah), which includes types such as ablution (وضوء - wudu), full washing (غسل - ghusl), and dry ablution (تيمم - tayammum). And purity from major impurities (حقيقية طهارة - haqiqiyyah taharah), and this definition of purity includes the purity of things that are not related to prayer, such as utensils and food. See: Fath Bab Al-Inayah 1: 41, and Al-Durr Al-Mukhtar wa Al-Rad Al-Mukhtar 1: 57, and Al-Badai 1: 2.