Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology the definition is more equivalent to fertility, or the actual reproductive rate of an organism or population, measured by the number of gametes (eggs), seed set or asexual propagules. This difference is due to the fact that demography considers human fecundity which is often intentionally limited, while biology assumes that organisms do not limit fertility. Fecundity is under both genetic and environmental control, and is the major measure of fitness. Fecundation is another term for fertilization. Super fecundity refers to an organism’s ability to store another organism’s sperm after copulation and fertilize its own eggs from that store after a period of time, essentially making it appear as though fertilization occurred without sperm.
Fecundity is important and well studied in the field of population ecology. Fecundity can increase or decrease in a population according to current conditions and certain regulating factors.
For instance, in times of hardship for a population such as a lack of food, juvenile and eventually adult fecundity has been shown to decrease.
Fecundity has also been shown to increase in ungulates with relation to warmer weather.
In the philosophy of science, fecundity refers to the ability of a scientific theory to open new lines of theoretical inquiry.
In sexual evolutionary biology, especially in sexual selection, fecundity is contrasted to reproductivity.
In obstetrics and gynaecology fecundability is the probability of being pregnant in a single menstrual cycle, Fecundity is the probability of achieving a live birth within a single cycle.