Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
Darwin coined the term fitness to refer to an organism’s relative ability to survive and produce fertile offspring. Nature selects the variations that are most useful. Therefore, he called this type of selection natural selection.


Question: Darwin coined what term to refer to an organism’s relative ability to survive and produce fertile offspring?
fitness
Fitness.