In the context of natural selection, what is a measure of the relative reproductive success of individuals?

Reproductive success of an individual is measured in term of its genetic contribution to the future generation as compared to that of other individuals of the same population.

Explanation:

Natural selection is the ability of some organisms to survive better and reproduce more due to the presence of some beneficial genetic traits. These individuals are able to leave more progeny as compared to the other individuals of the same population that lack those genetic traits. Therefore, reproductive success represents the ability of an organism to leave more progeny to contribute more to the gene pool of future generations.