Plural of fitness; multiple instances or types of the quality of being fit, healthy, or suitable for a particular purpose.
From 'fitness' (quality of being fit) plus the plural '-es,' since fitness ends in an s-sound. The root traces back to Middle English 'fit,' meaning suitable or appropriate.
Scientists in evolutionary biology talk about 'fitnesses' when comparing how well different organisms survive—each species has multiple ways to be 'fit' for their environment.
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