This paper defines a variety of fitness components, using a simple multidimensional hierarchical model that is consistent with recent definitions in the literature. It groups the definitions into two broad categories: product and process. Products refer to states of being such as physical fitness, health, and wellness. They are commonly referred to as outcomes and are frequently used as dependent measures in research. Process refers to behaviors or lifestyles, and these are frequently used as independent measures in research. First, the paper defines health-related fitness, focusing on body composition, cardiovascular fitness, flexibility, endurance, muscular endurance, and muscle strength. Next, it defines skill-related fitness, focusing on agility, balance, coordination, power, speed, and reaction time. It goes on to define physiological fitness, including metabolic fitness, morphological fitness, and bone integrity. The next section defines motor skills (non-fitness abilities that improve with practice and relate to the ability to perform specific sports and other motor tasks). The final section presents health definitions, including hypokinetic diseases or conditions, health, wellness, quality of life, healthy lifestyles or behaviors, physical activity, exercise, and leisure activity. (SM)