1. The state or condition of being fit; suitability or appropriateness.
2. Good health or physical condition, especially as the result of exercise and proper nutrition.
3. Biology. The extent to which an organism is adapted to or able to produce offspring in a particular environment.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.