Fertility is the natural capacity to produce offspring, whereas fecundity is the potential capacity for reproduction, according to Biology Online. Although the terms are often used interchangeably in common language, the Geneva Foundation for Medical Education and Research explains how they take on very distinct meanings when discussing matters of demographics and human population trends.
In biological discussion, fecundity and fertility have an extremely similar meaning. Biology Online defines fecundity as "a measure of fertility" and "the state of being fertile." Fertility is defined as "the capacity to induce conception and thus generate offspring."
According to Wikipedia, demographics scholars utilize the two terms to describe the unique phenomena that characterize human reproductive patterns. While animals do not intentionally limit their population growth, humans often employ contraception. Accordingly, human reproduction is limited by social, cultural and political factors in addition to biological factors.
The Geneva Foundation for Medical Education and Research explains that modern Western cultures often encourage women to seek careers before family life. As a result, women in these societies employ contraception and induced abortion, which lowers fecundity despite the absence of biological limitations to fertility. Political factors also play a role in fecundity. Public policies prescribing the legal number of children permitted to families lower national fecundity numbers even when members of the population are in good health.