The penis is a biological feature of male animals including both vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s (creatures with a backbone) and invertebrates. It is a reproductive, intromittent organ
Intromittent organ
An intromittent organ is a general term for an external organ of a male organism that is specialized to deliver sperm during copulation. Intromittent organs are found most often in terrestrial species, as most aquatic species fertilize their eggs externally, although there are...

 that additionally serves as the urinal duct
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...

 in placental mammals
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...



The word "penis" is taken from the Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 word for "tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

." Some derive that from Indo-European
Proto-Indo-European language
The Proto-Indo-European language is the reconstructed common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans...

 *pesnis, and the Greek word πέος = "penis" from Indo-European *pesos. Prior to the adoption of the Latin word in English the penis was referred to as a "yard". The Oxford English Dictionary
Oxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...

 cites an example of the word yard used in this sense from 1379, and notes that in his Physical Dictionary of 1684, Steven Blankaart
Steven Blankaart
Steven Blankaart , was a Dutch physician, Iatrochemist, and entomologist, who worked on the same field as Jan Swammerdam. Blankaart proved the existence of a capillary system, as had been suggested by Leonardo da Vinci, by spouting up bloodvessels, though he failed to realize the true significance...

 defined the word penis as "the Yard, made up of two nervous Bodies, the Channel, Nut, Skin, and Fore-skin, etc."

As with nearly any aspect of the body involved in sexual or excretory functions, the penis is the subject of taboo
A taboo is a strong social prohibition relating to any area of human activity or social custom that is sacred and or forbidden based on moral judgment, religious beliefs and or scientific consensus. Breaking the taboo is usually considered objectionable or abhorrent by society...

s, and there are many slang
Slang is the use of informal words and expressions that are not considered standard in the speaker's language or dialect but are considered more acceptable when used socially. Slang is often to be found in areas of the lexicon that refer to things considered taboo...

 words and euphemism
A euphemism is the substitution of a mild, inoffensive, relatively uncontroversial phrase for another more frank expression that might offend or otherwise suggest something unpleasant to the audience...

s for it, a particularly common and longstanding one being "cock
-Ornithology:* the male of most species of bird, but especially** A Rooster or cockerel, the male of the domestic fowl or chicken, Gallus domesticus*The English name of several species of bird incorporates the word cock, such as...


The Latin word "phallus
A phallus is an erect penis, a penis-shaped object such as a dildo, or a mimetic image of an erect penis. Any object that symbolically resembles a penis may also be referred to as a phallus; however, such objects are more often referred to as being phallic...

(from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 φαλλος) is sometimes used to describe the penis, although "phallus" originally was used to describe images, pictorial or carved, of the penis.

Pizzle is an old English word for penis, derived from Low German pesel or Flemish Dutch pezel, diminutive of pees 'sinew'. The word is used today to signify the penis of a non-human animal, now chiefly used in Australia and New Zealand...

, an archaic English word for penis, of Low German or Dutch origin, it is now used to denote the penis of a non human animal.

The adjectival form of the word penis is penile. This adjective is commonly used in describing various accessory structures of male copulatory organs found in many kinds of invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...



As with any other bodily attribute, the length and girth of the penis can be highly variable between individuals of the same species. In many animals, especially mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, the size of a flaccid penis is smaller than its erect size.

A bone called the baculum
The baculum is a bone found in the penis of most mammals. It is absent in humans, but present in other primates, such as the gorilla and chimpanzee.The bone aids in sexual intercourse.-Purpose:...

 or os penis is present in most mammals but absent in humans and horses.
Domesticated mammals

In domestic animals the penis is divided into three parts:
  • Roots (crura): these begin at the caudal border of the pelvic ischial arc.
  • Body: the part of the penis extending from the roots.
  • Glans: the free end of the penis.

The internal structures of the penis consist mainly of cavernous (erectile) tissue, which is a collection of blood sinusoids separated by sheets of connective tissue (trabeculae). Some animals have a lot of erectile tissue relative to connective tissue, for example horses. Because of this a horse's penis can enlarge more than a bull's penis. The urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...

 is on the ventral side of the body of the penis.

Stallions have a vascular penis. When non-erect, it is quite flaccid and contained within the prepuce (sheath). The retractor penis muscle is relatively underdeveloped. Erection and protrusion take place gradually, by the increasing tumescence of the erectile vascular tissue in the corpus cavernosum penis.

A bull has a fibro-elastic penis. There is a small amount of erectile tissue and a small amount of enlargement after erection. The penis is quite rigid when non-erect, and becomes even more rigid during erection. Protrusion is not affected much by erection, but more by relaxation of the retractor penis muscle and straightening out of the sigmoid flexure.

Dogs have a bulbus glandis at the base of their penis. During coitus the bulbus glandis swells up and results in a 'tie' (the male and female dogs being tied together). Muscles in the vagina of the female assist the retention by contracting.

The bull, ram and boar have a sigmoid flexure of their penis. This results in an S-shaped penis. It is straightened out during erection.
Other mammals

As a general rule, an animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

's penis is proportional to its body size, but this varies greatly between species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

even between closely related species. For example, an adult gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...

's erect penis is about 4 cm (1.5 in) in length; an adult chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

, significantly smaller (in body size) than a gorilla, has a penis size about double that of the gorilla. In comparison, the human
Humans are the only living species in the Homo genus...

 penis is larger than that of any other primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

, both in proportion to body size and in absolute terms.

In the realm of absolute size, the smallest vertebrate penis belongs to the Common Shrew
Common Shrew
The Common Shrew or Eurasian Shrew, Sorex araneus, is the most common shrew, and one of the most common mammals, throughout Northern Europe, including Great Britain, but excluding Ireland. It is long and weighs , and has velvety dark brown fur with a pale underside. Juvenile shrews have lighter...

 (5 mm or 0.2 inches). Accurate measurements of the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....

 are difficult to take because the whale's erect length can only be observed during mating.

Most marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...

s, except for the two largest species of kangaroo
A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...

s, have a bifurcated penis. That is, it separates into two columns, and so the penis has two ends corresponding to the females' two vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

s. Neither marsupials nor monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...

s possess a baculum.

Echidnas , also known as spiny anteaters, belong to the family Tachyglossidae in the monotreme order of egg-laying mammals. There are four extant species, which, together with the platypus, are the only surviving members of that order and are the only extant mammals that lay eggs...

s have a four-headed penis, but only two of the heads are used during mating. The other two heads "shut down" and do not grow in size. The heads used are swapped each time the mammal has sex.

Other vertebrates

Most male birds (e.g., rooster
A rooster, also known as a cockerel, cock or chanticleer, is a male chicken with the female being called a hen. Immature male chickens of less than a year's age are called cockerels...

s and turkey
Turkey (bird)
A turkey is a large bird in the genus Meleagris. One species, Meleagris gallopavo, commonly known as the Wild Turkey, is native to the forests of North America. The domestic turkey is a descendant of this species...

s) have a cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

 (also present on the female), but not a penis. Among bird species with a penis are paleognathes (tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....

s and ratites), Anatidae
Anatidae is the biological family of birds that includes ducks, geese and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica and on most of the world's islands and island groups...

 (ducks, geese and swans), and a very few other species (such as flamingo
Flamingos or flamingoes are gregarious wading birds in the genus Phoenicopterus , the only genus in the family Phoenicopteridae...

es). A bird penis is different in structure from mammal penises, being an erectile expansion of the cloacal wall and being erected by lymph
Lymph is considered a part of the interstitial fluid, the fluid which lies in the interstices of all body tissues. Interstitial fluid becomes lymph when it enters a lymph capillary...

, not blood. It is usually partially feathered and in some species features spines and brush-like filaments, and in flaccid state curls up inside the cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

. The Argentine Blue-bill
Argentine Blue-bill
The Lake Duck is a small South American stiff-tailed duck. It is also called the or Argentine Blue-bill, Argentine Lake Duck, or Argentine Ruddy Duck....

 has the largest penis in relation to body size of all vertebrates; while usually about half the body size (20 cm), a specimen with a penis 42.5 cm long is documented.

Male turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

s and crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

s have a penis, while male specimens of the reptile order Squamata
Squamata, or the scaled reptiles, is the largest recent order of reptiles, including lizards and snakes. Members of the order are distinguished by their skins, which bear horny scales or shields. They also possess movable quadrate bones, making it possible to move the upper jaw relative to the...

 have two paired organs called hemipenes
A hemipenis is one of a pair of intromittent organs of male squamates .Hemipenes are usually held inverted, within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. Only one is used at a time, and some evidence indicates males alternate use between...

. Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...

s must use their cloacae for reproduction.

In some fishes, the gonopodium, andropodium, and claspers are intromittent organs (to introduce sperm into the female) developed from modified fins.


The record for the largest penis to body size ratio is held by the barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...

. The barnacle's penis can grow to up to forty times its own body length. This enables them to reach the nearest female.

In male insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, the structure analogous to a penis is known as aedeagus
An aedeagus is a reproductive organ of male insects through which they secrete sperm from the testes during copulation with a female insect...

. The male copulatory organ of various lower invertebrate animals is often called the cirrus.

A number of invertebrate species have independently evolved the mating technique of traumatic insemination
Traumatic insemination
Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his penis and injects his sperm through the wound into her abdominal cavity . The sperm diffuse through the female's hemolymph,...

  where the penis penetrates the female's abdomen and deposits sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...

 in the wound it produces. This has been most fully studied in bedbug
Cimicidae are small parasitic insects. The most common type is Cimex lectularius. The term usually refers to species that prefer to feed on human blood...


Cultural uses

  • Culinary, particularly in Chinese gastronomy (such as dishes from the Guo Li Zhuang
    Guo Li Zhuang
    Guo Li Zhuang is a restaurant brand that specializes in dishes prepared from the genitals of male animals from a wide variety of species such as horse, ox, donkey, dog, deer, goat, sheep, and snake...

  • Magical and therapeutic, in medicine and/or superstition, especially as an alleged aphrodisiac or supposed cure for impotence – for example the deer penis
    Deer penis
    In traditional Chinese medicine, a deer penis is said to have important therapeutic properties. Deer penis and powdered deer penis is commonly sold in Chinese pharmacies. Like turtle's blood and penis, deer penis is also popular in Taiwan and is one of the "delicacies" served in large jars in...

     and tiger penis
    Tiger penis
    In traditional Chinese medicine, a tiger penis is said to have important therapeutic properties. However, modern science does not support the belief that the tiger penis possesses any special potency. Furthermore, the demand for tiger parts exacerbates the endangered status of the tiger by...

  • Punitive implements, such as the bull pizzle made into a form of whip
    A whip is a tool traditionally used by humans to exert control over animals or other people, through pain compliance or fear of pain, although in some activities whips can be used without use of pain, such as an additional pressure aid in dressage...

  • Dog chew toys, such as the bull pizzle (cut into short lengths for this purpose).

See also

  • Baculum
    The baculum is a bone found in the penis of most mammals. It is absent in humans, but present in other primates, such as the gorilla and chimpanzee.The bone aids in sexual intercourse.-Purpose:...

  • Bulbus glandis
    Bulbus glandis
    The bulbus glandis is an erectile tissue structure on the penis of canid mammals. During mating the tissues swell up and lock the male's penis inside the female. For domestic dogs the tie may last up to half an hour, though usually less....

  • Castration complex
  • Diphallia
    Diphallia, penile duplication , diphallic terata, or diphallasparatus, is a medical condition in which a male infant is born with two penises. This is an extremely rare disorder with only approximately 100 cases of diphallia recorded since the first, reported by Johannes Jacob Wecker in 1609...

  • Dildo
    A dildo is a sex toy, often explicitly phallic in appearance, intended for bodily penetration during masturbation or sex with partners.- Description and uses :...

  • Erogenous zone
    Erogenous zone
    An erogenous zone is an area of the human body that has heightened sensitivity, the stimulation of which may result in the production of erotic sensations or sexual excitement.People have erogenous zones all over their bodies, but which areas are more sensitive than others vary...

  • Koteka
    The koteka, horim, penis gourd or penis sheath is a phallocrypt or phallocarp traditionally worn by native male inhabitants of some ethnic groups in New Guinea to cover their genitals. They are normally made from a dried out gourd, Lagenaria siceraria, although other species, such as Nepenthes...

  • Micropenis
    Micropenis is an unusually small penis. A common criterion is a dorsal erect penile length of at least 2.5 standard deviations smaller than the mean human penis size. The condition is usually recognized shortly after birth...

  • Penis enlargement
    Penis enlargement
    Penis enlargement procedures are techniques alleged to make the human penis increase in girth, length, or hardness. Often, in the course of advertising fraudulent products, the distinction between temporary enlargement, i.e...

  • Penis envy
    Penis envy
    Penis envy in Freudian psychoanalysis refers to the theorized reaction of a girl during her psychosexual development to the realization that she does not have a penis....

  • Penis Plant
    Penis Plant
    The Penis Plant, also known as the Penis Cactus, is a monstrose form of Echinopsis lageniformis. This plant is more commonly referred to as Trichocereus bridgesii, even though the current scientific name is Echinopsis. Contrary to the typical columnar habit of the species, this cultivar displays...

  • Penis removal
    Penis removal
    In ancient civilizations, removal of the human penis was sometimes used as a means of demonstrating superiority: armies were sometimes known to sever the penises of their enemies to count the dead, as well as for trophies...

  • Phallus
    A phallus is an erect penis, a penis-shaped object such as a dildo, or a mimetic image of an erect penis. Any object that symbolically resembles a penis may also be referred to as a phallus; however, such objects are more often referred to as being phallic...

  • Preputial mucosa
    Preputial mucosa
    The preputial mucosa of the penis is the epithelium of the inside of the prepuce, or foreskin. To differentiate it from the cutaneous skin of the outside of the prepuce, it is sometimes referred to as the inner mucosa...

  • Preputioplasty
    Preputioplasty or prepuce plasty, also known as "limited dorsal slit with transverse closure", is a plastic surgical operation on the prepuce or foreskin of the penis, to widen a narrow non-retractile foreskin which cannot comfortably be drawn back off the head of the penis in erection because of a...

  • Pseudo-penis
    A pseudo-penis is a term used of any structure found on an animal that while superficially appearing to be a penis, is derived from a different developmental path.-Mammals:...

  • Pubic hair
    Pubic hair
    Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....

  • Stunt cock
    Stunt cock
    A stunt cock is the term for a substitute penis that is used during the shooting of pornographic films.The stunt cock is used in an extreme close up so as not to identify its bearer, the goal being to deceive the viewer into thinking that the stunt cock is actually the penis of the main actor...

  • Testicle
    The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...

  • Stamen
    The stamen is the pollen producing reproductive organ of a flower...

External links

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