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The symbol of the Roman goddess Venus is used to represent the female sex in biology. It also stands for the planet Venus and is the alchemical symbol for copper. Venus symbol.svg
The symbol of the Roman goddess Venus is used to represent the female sex in biology. It also stands for the planet Venus and is the alchemical symbol for copper.

Female (symbol: ) is the sex of an organism that produces the large non-motile ova (egg cells), the type of gamete (sex cell) that fuses with the male gamete during sexual reproduction. [2] [3] [4]


A female has larger gametes than a male. Females and males are results of the anisogamous reproduction system, wherein gametes are of different sizes, unlike isogamy where they are the same size. The exact mechanism of female gamete evolution remains unknown.

In species that have males and females, sex-determination may be based on either sex chromosomes, or environmental conditions. Most female mammals, including female humans, have two X chromosomes. Female characteristics vary between different species with some species having pronounced secondary female sex characteristics, such as the presence of pronounced mammary glands in mammals.

In humans, the word female can also be used to refer to gender in the social sense of gender role or gender identity. [5] [6]

Etymology and usage

"faemnan," an Old English word for 'female' Beowulf - faemnan.jpg
"fæmnan," an Old English word for 'female'

The word female comes from the Latin femella, the diminutive form of femina, meaning "woman". It is not etymologically related to the word male, but in the late 14th century the English spelling was altered to parallel that of male. [7] [8] Female is also used as a noun meaning "a female organism", though describing women as females is often considered disparaging, as it makes no distinction between other animals and humans. [9] [10]

Biological sex is conceptually distinct from gender, [11] [12] although they are often treated interchangeably. The adjective female can describe either a person's sex or gender identity. [13]

The word can also refer to the shape of connectors and fasteners, such as screws, electrical pins, and technical equipment. Under this convention, sockets and receptacles are called female, and the corresponding plugs male. [14] [15]

Defining characteristics

Females produce ova, the larger gametes in a heterogamous reproduction system, while the smaller and usually motile gametes, the spermatozoa, are produced by males. [3] [16] Generally, a female cannot reproduce sexually without access to the gametes of a male, and vice versa, but in some species females can reproduce by themselves asexually, for example via parthenogenesis. [17]

Patterns of sexual reproduction include:

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 moulds 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.[ citation needed ]

Females across species

Species that are divided into females and males are classified as gonochoric in animals, as dioecious in seed plants [20] and as dioicous in cryptogams. [21] :82

In some species, female and hermaphrodite individuals may coexist, a sexual system termed gynodioecy. [22] In a few species, female individuals coexist with males and simultaneous hermaphrodites; this sexual system is called trioecy. [23] In Thor manningi , primary[ clarification needed ] females coexist with primary males and protandrous hermaphrodites. [24]

Mammalian female

Photograph of an adult female human, with an adult male for comparison. Note that both models have partially shaved body hair to show anatomy; e.g. clean-shaven pubic regions. Anterior view of human female and male, with labels 2.png
Photograph of an adult female human, with an adult male for comparison. Note that both models have partially shaved body hair to show anatomy; e.g. clean-shaven pubic regions.

A distinguishing characteristic of the class Mammalia is the presence of mammary glands. Mammary glands are modified sweat glands that produce milk, which is used to feed the young for some time after birth. Only mammals produce milk. Mammary glands are obvious in humans, because the female human body stores large amounts of fatty tissue near the nipples, resulting in prominent breasts. Mammary glands are present in all mammals, although they are normally redundant in males of the species. [25]

Most mammalian females have two copies of the X chromosome, while males have only one X and one smaller Y chromosome; some mammals, such as the platypus, have different combinations. [26] [27] One of the female's X chromosomes is randomly inactivated in each cell of placental mammals while the paternally derived X is inactivated in marsupials. In birds and some reptiles, by contrast, it is the female which is heterozygous and carries a Z and a W chromosome while the male carries two Z chromosomes. In mammals, females can have XXX or X. [28] [29]

Mammalian females bear live young, with the exception of monotreme females, which lay eggs. [30] Some non-mammalian species, such as guppies, have analogous reproductive structures; and some other non-mammals, such as some sharks, also bear live young. [31]

In sex determination for mammals, female is the default sex, while in the poplar genus Populus the default is male. [32]

Sex determination

The sex of a particular organism may be determined by genetic or environmental factors, or may naturally change during the course of an organism's life. [22]

Genetic determination

The sex of most mammals, including humans, is genetically determined by the XY sex-determination system where males have X and Y (as opposed to X and X) sex chromosomes. During reproduction, the male contributes either an X sperm or a Y sperm, while the female always contributes an X egg. A Y sperm and an X egg produce a male, while an X sperm and an X egg produce a female. The ZW sex-determination system, where males have ZZ (as opposed to ZW) sex chromosomes, is found in birds, reptiles and some insects and other organisms. [22]

Environmental determination

The young of some species develop into one sex or the other depending on local environmental conditions, e.g. the sex of crocodilians is influenced by the temperature of their eggs. Other species (such as the goby) can transform, as adults, from one sex to the other in response to local reproductive conditions (such as a brief shortage of males). [33]


The question of how females evolved is mainly a question of why males evolved. The first organisms reproduced asexually, usually via binary fission, wherein a cell splits itself in half. From a strict numbers perspective, a species that is half males/half females can produce half the offspring an asexual population can, because only the females are having offspring. Being male can also carry significant costs, such as in flashy sexual displays in animals (such as big antlers or colorful feathers), or needing to produce an outsized amount of pollen as a plant in order to get a chance to fertilize a female. Yet despites the costs of being male, there must be some advantage to the process. [34]

The advantages are explained by the evolution of anisogamy, which led to the evolution of male and female function. [35] Before the evolution of anisogamy, mating types in a species were isogamous: the same size and both could move, catalogued only as "+" or "-" types. [36] In anisogamy, the mating cells are called gametes. The female gamete is larger than the male gamete, and usually immotile. [37] Anisogamy remains poorly understood, as there is no fossil record of its emergence. Numerous theories exist as to why anisogamy emerged. Many share a common thread, in that larger female gametes are more likely to survive, and that smaller male gametes are more likely to find other gametes because they can travel faster. Current models often fail to account for why isogamy remains in a few species. [34] Anisogamy appears to have evolved multiple times from isogamy; for example female Volvocales (a type of green algae) evolved from the plus mating type. [34] [38] Although sexual evolution emerged at least 1.2 billion years ago, the lack of anisogamous fossil records make it hard to pinpoint when females evolved. [39]

Female sex organs (genitalia, in animals) have an extreme range of variation among species and even within species. The evolution of female genitalia remains poorly understood compared to male genitalia, reflecting a now-outdated belief that female genitalia are less varied than male genitalia, and thus less useful to study. The difficulty of reaching female genitalia has also complicated their study. New 3D technology has made female genital study simpler. Genitalia evolve very quickly. There are three main hypotheses as to what impacts female genital evolution: lock-and-key (genitals must fit together), cryptic female choice (females affect whether males can fertilize them), and sexual conflict (a sort of sexual arms race). There is also a hypothesis that female genital evolution is the result of pleiotropy, i.e. unrelated genes that are affected by environmental conditions like low food also affect genitals. This hypothesis is unlikely to apply to a significant number of species, but natural selection in general has some role in female genital evolution. [40]


The symbol (Unicode: U+2640 Alt codes: Alt+12), a circle with a small cross underneath, is commonly used to represent females. Joseph Justus Scaliger once speculated that the symbol was associated with Venus, goddess of beauty because it resembles a bronze mirror with a handle, [41] but modern scholars consider that fanciful, and the most established view is that the female and male symbols derive from contractions in Greek script of the Greek names of the planets Thouros (Mars) and Phosphoros (Venus). [42] [43]

See also

Related Research Articles

<span class="mw-page-title-main">Asexual reproduction</span> Reproduction without a sexual process

Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Komodo dragons and some monitor lizards can also reproduce asexually.

<span class="mw-page-title-main">Gamete</span> Cell that fuses during fertilisation, such as a sperm or egg cell

A gamete is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that produces the larger type of gamete—called an ovum— and a male produces the smaller type—called a sperm. Sperm cells or spermatozoa are small and motile due to the flagellum, a tail-shaped structure that allows the cell to propel and move. In contrast, each egg cell or ovum is relatively large and non-motile. In short a gamete is an egg cell or a sperm. In animals, ova mature in the ovaries of females and sperm develop in the testes of males. During fertilization, a spermatozoon and ovum unite to form a new diploid organism. Gametes carry half the genetic information of an individual, one ploidy of each type, and are created through meiosis, in which a germ cell undergoes two fissions, resulting in the production of four gametes. In biology, the type of gamete an organism produces determines the classification of its sex.

<span class="mw-page-title-main">Reproduction</span> Biological process by which new organisms are generated from one or more parent organisms

Reproduction is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. There are two forms of reproduction: asexual and sexual.

<span class="mw-page-title-main">Sex</span> Trait that determines an individuals sexually reproductive function

Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes, while females produce larger ones. Organisms that produce both types of gametes are called hermaphrodites. During sexual reproduction, male and female gametes fuse to form zygotes, which develop into offspring that inherit traits from each parent.

<span class="mw-page-title-main">Sex organ</span> Body part involved in sexual reproduction

A sex organ is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, are called the primary sex organs. All others are called secondary sex organs, divided between the external sex organs—the genitals or externalgenitalia, visible at birth in both sexes—and the internal sex organs.

<span class="mw-page-title-main">XY sex-determination system</span> Method of determining sex in all animals

The XY sex-determination system is a sex-determination system used to classify many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants. In this system, the sex of an individual is determined by a pair of sex chromosomes. Females have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males have two different kinds of sex chromosomes (XY), and are called the heterogametic sex.

<span class="mw-page-title-main">Sex-determination system</span> Biological system that determines the development of organism’s sex

A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes.

<span class="mw-page-title-main">Sexual differentiation</span> Embryonic development of sex differences

Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.

In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric.

<span class="mw-page-title-main">Anisogamy</span> Sexual reproduction involving a large, female gamete and a small, male gamete

Anisogamy is a form of sexual reproduction that involves the union or fusion of two gametes that differ in size and/or form. The smaller gamete is male, a sperm cell, whereas the larger gamete is female, typically an egg cell. Anisogamy is predominant among multicellular organisms. In both plants and animals gamete size difference is the fundamental difference between females and males.

<span class="mw-page-title-main">Isogamy</span>

Isogamy is a form of sexual reproduction that involves gametes of the same morphology, found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or female. Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as "+" and "−" strains.

Reproductive biology includes both sexual and asexual reproduction.

<span class="mw-page-title-main">Male</span> Sex of an organism which produces sperm

Male is the sex of an organism that produces the gamete known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization.

<span class="mw-page-title-main">XO sex-determination system</span> Biological system that determines the sex of offspring

The XO sex-determination system is a system that some species of insects, arachnids, and mammals use to determine the sex of offspring. In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (XO), while females have two (XX). The letter O signifies the lack of a second X. Maternal gametes always contain an X chromosome, so the sex of the animals' offspring depends on whether a sex chromosome is present in the male gamete. Its sperm normally contains either one X chromosome or no sex chromosomes at all.

Mating types are the microorganism equivalent to sexes in multicellular lifeforms and are thought to be the ancestor to distinct sexes. They also occur in macro-organisms such as fungi.

<span class="mw-page-title-main">Sexual differentiation in humans</span> Process of development of sex differences in humans

Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts and body hair plays a role in sex identification.

<span class="mw-page-title-main">Hermaphrodite</span> Organism that has complete or partial male and female reproductive organs

In reproductive biology, a hermaphrodite is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.

The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. 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.

<span class="mw-page-title-main">Sexual reproduction</span> Reproduction process that creates a new organism by combining the genetic material of two organisms

Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.

<span class="mw-page-title-main">Mammalian reproduction</span> Most mammals are viviparous, giving birth to live young

Most mammals are viviparous, giving birth to live young. However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian mammal.


  1. Stearn, William T. (17 August 1961). "The Male and Female Symbols of Biology". New Scientist . 11 (248): 412–413. LCCN   59030638.
  2. Grzimek, Bernhard (2003). Grzimek's Animal Life Encyclopedia. Vol. 1. Gale. pp. 16–17. ISBN   978-0-7876-5362-0. During sexual reproduction, each parent animal must form specialized cells known as gametes...In virtually all animals that reproduce sexually, the gametes occur in two morphologically distinct forms corresponding to male and female. These distinctions in form and structure are related to the specific functions of each gamete. The differences become apparent during the latter stages of spermatogenesis (for male gametes) and oogenesis (for female gametes)....After oogenetic meiosis, the morphological transformation of the female gamete generally includes development of a large oocyte that does not move around....The ambiguous term "egg" is often applied to oocytes and other fertilizable stages of female gametes....Spermatogenesis and oogenesis most often occur in different individual animals known as males and females respectively.
  3. 1 2 Martin, Elizabeth; Hine, Robert (2015). A Dictionary of Biology. Oxford University Press. p. 222. ISBN   978-0-19-871437-8. Female 1. Denoting the gamete (sex cell) that, during sexual reproduction, fuses with a male gamete in the process of fertilization. Female gametes are generally larger than the male gametes and are usually immotile (see Oosphere; Ovum). 2. (Denoting) an individual organism whose reproductive organs produce only female gametes.
  4. Fusco, Giuseppe; Minelli, Alessandro (2019-10-10). The Biology of Reproduction. Cambridge University Press. pp. 111–113. ISBN   978-1-108-49985-9.
  5. L. Gordon, "On difference", in Genders (1991), p. 95
  6. Laura Palazzani, Gender in Philosophy and Law (2012), page v
  7. Online Etymology Dictionary - Female (n.) Retrieved 2019-11-24
  8. Donald M. Ayers, English Words from Latin and Greek Elements, second edition (1986, University of Arizona Press), p. 113
  9. "Using 'Lady,' 'Woman,' and 'Female' to Modify Nouns". www.merriam-webster.com. Retrieved 2022-08-04.
  10. "Misconceptions about evolution – Understanding Evolution". 19 September 2021. Archived from the original on 6 June 2022. Retrieved 21 May 2022.
  11. "Gender and Genetics". WHO. Archived from the original on November 11, 2012. Retrieved 2020-07-31.
  12. "Sex & Gender". Office of Research on Women's Health. Archived from the original on 2020-07-23. Retrieved 2020-07-31.
  13. "Definition of FEMALE". www.merriam-webster.com. Retrieved 2022-08-04.
  14. J. Richard Johnson, How to Build Electronic Equipment (1962), p. 167: "To minimize confusion, the connector portions with projecting prongs are referred to as the 'male' portion, and the sockets as the 'female' portion."
  15. Richard Ferncase, Film and Video Lighting Terms and Concepts (2013), p. 96: "female[:] Refers to a socket type connector, which must receive a male connector"
  16. David E. Sadava, H. Craig Heller, William K. Purves, Life: The Science of Biology (2008), p. 899
  17. Franz Engelmann, G. A. Kerkut, The Physiology of Insect Reproduction (2015), p. 29
  18. Kumar R, Meena M, Swapnil P (2019). "Anisogamy". In Vonk J, Shackelford T (eds.). Anisogamy. Encyclopedia of Animal Cognition and Behavior. Cham: Springer International. pp. 1–5. doi:10.1007/978-3-319-47829-6_340-1. ISBN   978-3-319-47829-6.
  19. Dusenbery, David B. (2009). Living at Micro Scale, Chapter 20. Harvard University Press, Cambridge, Massachusetts ISBN   978-0-674-03116-6.
  20. Fusco, Giuseppe; Minelli, Alessandro (2019-10-10). The Biology of Reproduction. Cambridge University Press. pp. 115–116. ISBN   978-1-108-49985-9.
  21. Buck WR & Goffinet B (August 2000). "Morphology and classification of mosses". In Shaw AJ & Goffinet B (ed.). Bryophyte Biology. New York: Cambridge University Press. ISBN   978-0-521-66794-4.
  22. 1 2 3 Bachtrog D, Mank JE, Peichel CL, Kirkpatrick M, Otto SP, Ashman TL, et al. (July 2014). "Sex determination: why so many ways of doing it?". PLOS Biology. 12 (7): e1001899. doi:10.1371/journal.pbio.1001899. PMC   4077654 . PMID   24983465.
  23. Leonard, Janet L. (2019-05-21). Transitions Between Sexual Systems: Understanding the Mechanisms of, and Pathways Between, Dioecy, Hermaphroditism and Other Sexual Systems. Springer. p. 23. ISBN   978-3-319-94139-4.
  24. Fusco, Giuseppe; Minelli, Alessandro (2019-10-10). The Biology of Reproduction. Cambridge University Press. pp. 133–135. ISBN   978-1-108-49985-9.
  25. Swaminathan, Nikhil. "Strange but True: Males Can Lactate". Scientific American.
  26. Adrian T. Sumner, Chromosomes: Organization and Function (2008), pp. 97-98
  27. Benjamin A. Pierce, Genetics: A Conceptual Approach (2012), p. 73
  28. John R. McCarrey, Ursula K. Abbott, "Sex Determination in Animals", in Advances in Genetics (1979), volume 20, pages 219-220
  29. Hake, Laura; O'Connor, Clare. "Genetic Mechanisms of Sex Determination". Nature Education. 1 (1): 25. Retrieved 2021-04-13.
  30. Terry Vaughan, James Ryan, Nicholas Czaplewski, Mammalogy (2011), pp. 391, 412
  31. Quentin Bone, Richard Moore, Biology of Fishes (2008), page 234
  32. Cronk, Quentin; Müller, Niels A. (2020-07-29). "Default Sex and Single Gene Sex Determination in Dioecious Plants". Frontiers in Plant Science. 11: 1162. doi: 10.3389/fpls.2020.01162 . ISSN   1664-462X. PMC   7403218 . PMID   32849717.
  33. Gemmell, Neil J.; Muncaster, Simon; Liu, Hui; Todd, Erica V. (2016). "Bending Genders: The Biology of Natural Sex Change in Fish". Sexual Development. 10 (5–6): 223–241. doi: 10.1159/000449297 . ISSN   1661-5425. PMID   27820936.
  34. 1 2 3 Togashi, Tatsuya; Cox, Paul Alan (2011-04-14). The Evolution of Anisogamy: A Fundamental Phenomenon Underlying Sexual Selection. Cambridge University Press. pp. 1–15. ISBN   978-1-139-50082-1.
  35. Bachtrog, Doris; Mank, Judith E.; Peichel, Catherine L.; Kirkpatrick, Mark; Otto, Sarah P.; Ashman, Tia-Lynn; Hahn, Matthew W.; Kitano, Jun; Mayrose, Itay; Ming, Ray; Perrin, Nicolas (2014-07-01). "Sex Determination: Why So Many Ways of Doing It?". PLOS Biology. 12 (7): e1001899. doi:10.1371/journal.pbio.1001899. ISSN   1545-7885. PMC   4077654 . PMID   24983465.
  36. Sawada, Hitoshi; Inoue, Naokazu; Iwano, Megumi (2014). Sexual Reproduction in Animals and Plants. Springer. p. 216. ISBN   978-4-431-54589-7.
  37. Kumar R, Meena M, Swapnil P (2019). "Anisogamy". In Vonk J, Shackelford T (eds.). Anisogamy. Encyclopedia of Animal Cognition and Behavior. Cham: Springer International. pp. 1–5. doi:10.1007/978-3-319-47829-6_340-1. ISBN   978-3-319-47829-6.
  38. Sawada, Hitoshi; Inoue, Naokazu; Iwano, Megumi (2014-02-07). Sexual Reproduction in Animals and Plants. Springer. p. 222. ISBN   978-4-431-54589-7.
  39. Butterfield, Nicholas J. (2000). "Bangiomorpha pubescens n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes". Paleobiology . 26 (3): 386. doi:10.1666/0094-8373(2000)026<0386:BPNGNS>2.0.CO;2. S2CID   36648568 . Retrieved 12 April 2021.
  40. Sloan, Nadia S.; Simmons, Leigh W. (2019). "The evolution of female genitalia". Journal of Evolutionary Biology. 32 (9): 882–899. doi: 10.1111/jeb.13503 . ISSN   1420-9101. PMID   31267594.
  41. Taylor, Robert B. (2016), "Now and Future Tales", White Coat Tales, Springer International Publishing, pp. 293–310, doi:10.1007/978-3-319-29055-3_12, ISBN   978-3-319-29053-9
  42. Stearn, William T. (May 1962). "The Origin of the Male and Female Symbols of Biology". Taxon. 11 (4): 109–113. doi:10.2307/1217734. JSTOR   1217734. S2CID   87030547. The origin of these symbols has long been of interest to scholars. Probably none now accepts the interpretation of Scaliger that represents the shield and spear of Mars and Venus's looking glass.
  43. G D Schott, Sex, drugs, and rock and roll: Sex symbols ancient and modern: their origins and iconography on the pedigree, BMJ 2005;331:1509-1510 (24 December), doi : 10.1136/bmj.331.7531.1509