noun: fitness
1.
the condition of being physically fit and healthy.
"disease and lack of fitness are closely related"
synonyms:health, strength, robustness,sturdiness, hardiness, vigour,lustiness, stalwartness;
athleticism,toughness, ruggedness, physical fitness, muscularity, tone;
good health, good condition, good shape,well-being;
state of health, condition,shape, trim, fettle;
BIOLOGY
an organism's ability to survive and reproduce in a particular environment.
plural noun: fitnesses
"if sharp teeth increase fitness, then genes causing teeth to be sharp will increase in frequency"
2.
the quality of being suitable to fulfil a particular role or task.
"the medical board assessed his fitness for active service"
"he was called before medical boards to assess his fitness for active service"