HEALTH is a condition that describes how effectively you are able to function. It changes with the circumstances of your life, and therefore, calls for modifications in your lifestyle.
WELLNESS means optimal health.
It is something achieved or maintained essentially with a positive approach to life. Definitely, being healthy is more than not being sick, good health in fact, allows you to realize your full potential.
Wellness promotes the idea that, while aging may diminish certain capabilities, it does not have to take away from quality of life. Optimal health begins with the awareness that many illnesses associated with aging can be prevented.
Excerpt from FPHC's Corporate Wellness