Heritability
Defined as the proportion of the total variation in a population which is due to genotypic (as opposed to environmental) factors. Often denoted as h2. Because it is a proportion, it varies between 0 and 1.
Broad sense heritability includes includes additive, dominant and epistatic effects. Narrow-sense heritability includes only additive variation.
If h2 = 0, none of the variation is genotypic, it is all due to variation in the environment
If h2 is small, the trait is strongly influenced by the environment – e.g., yield
If h2 is large, the trait is only slightly influenced by the environment (e.g. flower colour).