To do its broader meaning justice, the most basic characteristics of the general concept of diversity measurement are compiled, and a class of measures complying with the conditions of the concept is presented. Application to the measurement of genetic variation shows that, in particular, the common notion of genic diversity for multiple loci suffers from vagueness. An attempt towards clarification and resolution of the problem is made via redefinition of the elements of the gene pool. It is found that extension of single-locus (allelic) diversities to multiple loci by taking the mean over loci is inadequate. After computing the theoretical bounds for the proportion of heterozygotes given the underlying allelic frequencies within a population, it is concluded that in many cases intra-populational heterozygosity is completely unrelated to genic diversity. On the other hand, in comparing diversities of different populations, two kinds of theoretical inter-populational heterozygosity play a central role in illuminating its relationship to genetic distance between populations. On this occasion, it turns out that one particular measure of genetic distance reflects directly an important minimum property of heterozygosity.
