Health is the general condition of a person in all aspects. It is also a level of functional and/or metabolic efficiency of an organism, often implicitly human.

Sport is an activity that is governed by a set of rules or customs and often engaged in competitively. Sports are most often played just for fun or for the simple fact that people need exercise to stay in good physical condition.

Fitness, ie. Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health.

Sources: Wikipedia