This document discusses the history and definitions of health. It notes that the word "health" originated from an Old English word meaning sound and safe. Three major concepts of health are identified: (1) the traditional medical concept of health as the absence of disease, (2) the WHO's holistic concept of complete physical, mental and social well-being, and (3) more ecological notions emphasizing relationships between individuals and their environments. The document then examines definitions and aspects of physical, mental, social, and spiritual health.