(1) The tendency of individual genetic characteristics in a population to vary from one another.
(2) The potential of a genotype to change or deviate when exposed to environmental or genetic factors.
Genetic variability is different from genetic diversity (or genetic variation) in a way that the former measures how much the trait or the genotype will tend to vary whereas the latter measures the number of the actual variation of species in a population. Compared with genetic diversity, genetic variability is more difficult to measure. At the molecular level, genetic variability may be measured by determining the rate of mutation.