Health is defined in the WHO (World Health Organization) constitution of 1948 as: a state of complete physical, social and mental well-being, and not merely the absence of disease or infirmity.

Hygiene is the science of preventing and protecting the health of people through control of the Environment.

Environment is our surroundings described as physical surroundings (air, water and land), biological surroundings (animals and plants), and social surroundings.