What Is Health? What Does Good Health Mean?

As defined by WHO  (World Health Organization), it is a "State of complete physical, mental, and social well being, and not merely the absence of disease or infirmity."

On the other hand, if you hear the phrase "With all these deadlines, presentations and working weekends, I wonder what the effect will be on her health," most likely the word "health" refers more to mental health than physical health (although the two are often linked).

The words "health" or "healthy" can also be used in non-medical contexts. For example "A healthy economy needs an ideal GDP growth rate that is sustainable, one that remains in the expansion phase of the business cycle as long as possible."
World Health Organization's (WHO's) definition of "health"

The most famous modern definition of health was created during a Preamble to the Constitution of the World Health Organization as adopted by the International Health Conference, New York, 19-22 June, 1946; signed on 22 July 1946 by the representatives of 61 States (Official Records of the World Health Organization, no. 2, p. 100) and entered into force on 7 April 1948.

The word health means different things to different people, depending on the situation. If somebody says "I was worried about my husband's health when he climbed Mt. Everest", it is clear that the woman is referring to her husband's physical health, possibly his heart, skin (frostbite) and risk of developing hypothermia (when the body's temperature drops too low.Health is a dynamic condition resulting from a body's constant adjustment and adaptation in response to stresses and changes in the environment for maintaining an inner equilibrium called homeostasis.