The most accurate measurement of the human penis comes from several measurements at different times since there is natural minor variability in size due to arousal level, time of day, room temperature, frequency of sexual activity, and reliability of measurement. When compared to other primates, including large primates such as the gorilla, the human penis is largest, both in absolute terms and in relative size to the rest of the body.
Measurements vary, with studies that rely on self-measurement reporting a significantly higher average than those with staff measuring. However, the mean of an erect human penis is approximately 12.9–15.0 cm (5.1–5.9 in) in length. Flaccid penis length is a poor estimate of erect length.
The reproductive system or genital system is a system of sex organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system.[dead link] Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.
A sex organ or primary sexual characteristic, as narrowly defined, is any anatomical part of the body involved in sexual reproduction and constituting the reproductive system in a complex organism, especially the external sex organs; the external sex organs are also commonly referred to as the genitalia or genitals.
Flowers are the reproductive organs of flowering plants, cones are the reproductive organs of coniferous plants, whereas mosses, ferns, and other similar plants have gametangia for reproductive organs.