Female (♀) is the sex of an organism, or a part of an organism, which produces ova (egg cells). The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male. A female individual cannot reproduce sexually without access to the gametes of a male (an exception is parthenogenesis). Some organisms can reproduce both sexually and asexually.
There is no single genetic mechanism behind sex differences in different species and the existence of two sexes seems to have evolved multiple times independently in different evolutionary lineages. Other than the defining difference in the type of gamete produced, differences between males and females in one lineage cannot always be predicted by differences in another. The concept is not limited to animals; egg cells are produced by chytrids, diatoms, water molds and land plants, among others. In land plants, female and male designate not only the egg- and sperm-producing organisms and structures, but also the structures of the sporophytes that give rise to male and female plants.
The word female comes from the Latin femella, the diminutive form of femina, meaning "woman," which is not actually related to the word "male." The word was probably originally femella, meaning "young girl." In the late 14th century, the English spelling was altered so that the word paralleled the spelling of "male."
The phrase the female, in the sense of the female sex or the class of all women, figures prominently in the first act of Henry V, in which Henry's bishops discuss with him the right of the French King to his throne—and Henry's right to usurp it. They conclude that the salic law cited by the French is not really French, but German, and that Henry can properly invade France, thus prolonging the Hundred Years' War.
The distinguishing characteristic of the class Mammalia is the presence of mammary glands. The mammary glands are modified sweat glands that produce milk, which is used to feed the young during the period of time shortly after birth. Only mammals have the capacity to produce milk. The presence of mammary glands is most obvious on humans, due to the tendency of the female human body to store large amounts of fatty tissue near the nipples, resulting in prominent breasts, although today some human females also surgically augment their breast size. However, mammary glands are present in all mammals, although they are vestigial in the male of the species.
The mammalian female is characterized by having two copies of the X chromosome as opposed to the male which carries only one X and one smaller Y chromosome. To compensate for the difference in size, one of the female's X chromosomes is randomly inactivated in each cell. In birds, by contrast, it is the female who is heterozygous and carries a Z and a W chromosome whilst the male carries two Z chromosomes.
Mammalian females are also unique in that they all bear live young (with the rare exception of monotremes, which lay eggs). However, there are non-mammalian animals (such as sharks) whose eggs hatch inside their bodies, which gives the appearance that they bear live young.
The sex of a particular organism may be determined by a number of factors. These may be genetic or environmental, or may naturally change during the course of an organism's life. Although most species with male and female sexes have individuals that are either male or female, hermaphroditic animals have both male and female reproductive organs.
Some species develop into one sex or the other depending on local environmental conditions, e.g. many crocodilians' sex is influenced by the temperature of their eggs. Other species (such as the goby) are capable of transforming, as adults, from one sex to the other in response to local reproductive conditions (such as a shortage of males). In humans and most mammals, sex is determined chromosomally -- a Y sperm will produce a male offspring and an X sperm a female.