Fertility is the natural capability to produce offspring. As a measure, fertility rate is the number of offspring born per mating pair, individual or population. Fertility differs from fecundity, which is defined as the potential for reproduction (influenced by gamete production, fertilization and carrying a pregnancy to term) A lack of fertility is infertility while a lack of fecundity would be called sterility.
Human fertility depends on factors of nutrition, sexual behavior, consanguinity, culture, instinct, endocrinology, timing, economics, way of life, and emotions.