fitness

American  

[fit-nis] / ˈfɪt nɪs /

noun

1. health.

2. capability of the body of distributing inhaled oxygen to muscle tissue during increased physical effort.

3. Also called Darwinian fitness.  Biology.

   1. the genetic contribution of an individual to the next generation's gene pool relative to the average for the population, usually measured by the number of offspring or close kin that survive to reproductive age.

   2. the ability of a population to maintain or increase its numbers in succeeding generations.

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fitness British  

/ ˈfɪtnɪs /

noun

1. the state of being fit

2. biology

   1. the degree of adaptation of an organism to its environment, determined by its genetic constitution

   2. the ability of an organism to produce viable offspring capable of surviving to the next generation

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Etymology

Origin of fitness

First recorded in 1570–80; fit ¹ + -ness

Explanation

Fitness is good physical condition. If you're a fitness nut and you're constantly working out, everybody else at the gym might be eyeing your sculpted muscles with envy and marveling at your stamina and strength. Fitness can also refer to your being fit, or qualified, for something. If you show up in ragged jeans and a dirty t-shirt to interview for a job in the clean room of a microchip factory, your interviewer might question your fitness for the position. For a ship, fitness is a measure of whether it's seaworthy. In biology, an organism's fitness for a particular environment is its ability to survive and reproduce in those conditions.

Example Sentences

Sion, 38, from Porthmadog, Gwynedd, began his fitness journey in 2013 after his first year at university in Liverpool.

From BBC • Apr. 10, 2026

Young people view wellness spending as essential and use fitness to meet new people and maintain friendships.

From The Wall Street Journal • Apr. 10, 2026

The monthly fee, similar to a condo’s HOA fee, covers things like maintenance services, dining, utilities and access to campus amenities like the fitness center and indoor swimming pool.

From MarketWatch • Apr. 10, 2026

Striker Dominic Solanke was also sidelined for months with an ankle injury while Xavi Simons has also struggled with fitness in his debut season in England.

From BBC • Apr. 10, 2026

Glenn’s training was very rigorous, including his physical fitness.

From "Reaching for the Moon" by Katherine Johnson

Related Words

• adequacy
• compatibility
• competence
• consistency
• eligibility
• preparedness
• qualification
• readiness
• suitability