Sociologists define religion in three main ways - substantive, functional, and social constructionist. Substantive definitions focus on religious beliefs like belief in God or the supernatural. Functional definitions see religion as serving social or psychological functions. Social constructionist definitions say religion cannot be universally defined and definitions are contested and influenced by those in power. Durkheim saw religion as reinforcing social solidarity through rituals and collective worship. Malinowski and Parsons argued religion helps individuals cope with stress and finds meaning. Bellah's concept of civil religion described religion uniting American society through rituals like pledging allegiance. Lenin and Marx viewed religion as a tool for ruling classes to control populations by masking exploitation.