the male, female, or sometimes intersex division of a species, especially as differentiated with reference to the reproductive functions or physical characteristics such as genitals, XX and XY chromosomes, etc.
a label assigned to a person at birth, usually male or female and sometimes intersex, and typically based on genital configuration.
the sum of the structural and functional differences by which male, female, and sometimes intersex organisms are distinguished, or the phenomena or behavior dependent on these differences.
These plants change sex depending on how much light they receive.
sexual relations or activity, especially sexual intercourse.
We hold a large collection of oral histories that explore changing attitudes to sex and marriage.
the sexual instinct or attraction drawing one organism toward another, or its manifestation in life and conduct.
Some disapprove of choosing a life partner based on sex.
the genitals; genitalia.
A towel was hiding his sex from view.
the sum of the characteristics that distinguish organisms on the basis of their reproductive function
either of the two categories, male or female, into which organisms are placed on this basis
short for sexual intercourse
feelings or behaviour resulting from the urge to gratify the sexual instinct
sexual matters in general
of or concerning sexual matters
sex education
sex hygiene
based on or arising from the difference between the sexes
sex discrimination
Human sex is often seen as strictly binary and composed only of male and female. It is certainly true that, when it comes to reproduction, there are two different cell types that combine to form an embryo: the sperm and the egg. People who think of sex as binary often assume that sex simply reflects whether a person produces eggs or sperm. In practice, however, the way that a person's sex is categorized depends on several characteristics: genitals, chromosomes, hormonal profiles, and external physical features such as the development of extensive facial hair or breast tissue. These characteristics do frequently occur together. For example, the majority of people born with XX chromosomes are also born with ovaries that produce eggs, and most also go on to develop more breast tissue during puberty. Male and female, when used of sex, usually refer to people who fit more or less into these common patterns of co-occurring characteristics. However, there are people born with physical characteristics that do not fit neatly into these categories. For example, some people have XY chromosomes, but their cells cannot respond to androgens, meaning that they may develop a vagina and more breast tissue. Others are born with gonads that do not produce either sperm or egg cells. There are also people born with chromosomes that are XXY. Such conditions may be called intersex conditions, disorders of sex development, or differences of sex development. These terms are broad labels that do not constitute a discrete third sex, but rather identify variation in physical characteristics that does not fit into the male-female binary. Like anyone else, a person with any of these conditions may identify as a man, a woman, or any other gender. Furthermore, a person's sex characteristics may or may not influence their gender, or their relationship with their gender. See gender 1, intersex.
What does sex- mean? Sex- is a combining form used like a prefix meaning “six.” It appears occasionally in technical terms, especially in mathematics. Sex- comes from Latin sex, meaning “six.” Yes, “six.” Discover why at our entry for six. Another combining form meaning "six" is hexa-, which comes from Greek héx. Learn more at our Words That Use entry for hexa-. What are variants of sex-?Sex- is a variant of sexi-, which sometimes loses its -i- when combined with words or word elements beginning with vowels. Want to know more? Read our Words That Use sexi- article.
Thanks to high school biology, we are accustomed to thinking of the sex of an organism as being determined by the chromosomes, notably the sex chromosome in humans (designated X or Y). But this is not the whole story, and it applies universally only to mammals and birds. In other animals sex is often determined by environmental factors and can be a variable phenomenon. In a species of slipper limpet (Crepidula fornicata), a kind of mollusk, all individuals begin life as females. Clinging to rocks and to each other, they form piles. The limpet on top of the pile changes into a male. If another limpet attaches itself on top of the male limpet, the newcomer becomes male, and the male limpet beneath it reverts to being female. These slipper limpets show the evolutionarily advanced feature of internal fertilization, and the male on top extends his reproductive organ down the pile of females below him to fertilize their eggs. For some fish, the number of males in the population determines the sex of the fish. If there are not enough males, some females become males. In these examples, the same animal can make fertile eggs and fertile sperm at different times in its life. These animals are not hermaphrodites, like some worms, but literally change sex. Some animals have only one sex. For instance, some species of lizards reproduce only by parthenogenesis—that is, their unfertilized eggs grow into adults, and these species no longer have males. Sometimes the external temperature determines the sex of an animal during its early development. If the eggs of the American alligator (Alligator mississippiensis) are incubated at above 34 degrees Celsius (93° F), all of the offspring become males. If they are incubated below 30 degrees Celsius (86° F), they become females. The midrange of temperatures results in both male and female offspring.
First recorded in 1350–1400; Middle English, from Latin sexus, perhaps akin to secāre “to divide” ( see section)
< Latin, combining form of sex six
If you're looking to adopt a cat, you might ask the volunteer at the shelter about that little orange kitten's age and sex. Sex refers to whether the cat is male or female. In addition to referring to the biological categories of male and female, sex is also shorthand for the activity of being physically intimate with a romantic partner. This word can also be used as a verb: farmers who sex their chickens are figuring out whether they have a rooster or a hen.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The researchers compared 38 people with severe aortic stenosis with 38 control participants matched for factors including age, sex, and major medical conditions.
From Science Daily ● Jul. 12, 2026
But it's not just biology that puts us more at risk, said Dr Pinho-Gomes, co-author of a review into sex differences in heatwave-associated deaths, external.
From BBC ● Jul. 8, 2026
But “Gail Daughtry” is less about sex and personal empowerment than the cult of celebrity.
From Los Angeles Times ● Jul. 8, 2026
So why does every study show that Gen Z drinks less, breaks fewer bones, has less sex and goes on fewer dates?
From The Wall Street Journal ● Jul. 7, 2026
How did bees ever become equated with sex?
From "The Secret Life of Bees" by Sue Monk Kidd
Today, she believes, “If we can move from an androcentric, anthropocentric view to a sex-, gender-, and species-spanning perspective, then we can do good.”
From Los Angeles Times ● Oct. 14, 2022
NSO Group does not disclose its clients and says it sells its technology to Israeli-approved governments to help them target terrorists and break up pedophile rings and sex- and drug-trafficking rings.
From Seattle Times ● Jul. 18, 2021
At its annual meeting last week, the agency adopted a requirement that, when relevant, grant applicants outline any sex- and gender-related aspects of their research in their proposals.
From Nature ● Jul. 10, 2018
Adapted from David Ebershoff’s novel, it is loosely based on the life of Lili Elbe, who died in 1933 after one of the first sex- reassignment surgeries.
From The Guardian ● Feb. 2, 2018
"Loveliest of thy sex-" he began; but I forced myself from him and ran upstairs.
From Evelina, Or, the History of a Young Lady's Entrance into the World by Burney, Fanny
In fact, the author argues that, contra the “biological essentialist” view that says women are made for child care and men for professional work, the sexes are actually more similar than they are different.
From The Wall Street Journal ● Jul. 8, 2026
No one disputes that there are physical differences between the sexes.
From Los Angeles Times ● Jul. 7, 2026
That affects both sexes, he added, but said there were "particular issues for boys".
From BBC ● Jun. 5, 2026
"Treatment outcomes were consistent and similar across both sexes."
From Science Daily ● May 26, 2026
She learned that there were two sexes, and that they lived monogamously in couples.
From "The Amber Spyglass" by Philip Pullman
The pups, who are yet to be named or sexed, will begin emerging from the den at around three months old before taking their first exploratory swims.
From BBC ● Feb. 19, 2025
The space and resources dedicated to roosters at animal sanctuaries are often devoted to backyard chickens that were improperly sexed.
From New York Times ● Jan. 18, 2023
Last year, a paper published in Scientific Reports showed that, contrary to prior understanding, softshell turtles possess sex chromosomes, which means that they can be sexed using DNA analysis.
From The New Yorker ● Dec. 24, 2018
A series of swift, scientific maneuvers followed: The researchers measured, sexed and appraised the animal.
From Seattle Times ● Jun. 6, 2017
Individuals smaller than 100 mm. ordinarily could not be sexed accurately and are shown as open bars.
From Natural History of the Ornate Box Turtle, Terrapene ornata ornata Agassiz by Legler, John M.
Several European countries use the technology, known as in-ovo sexing, which can determine the sex of a chick before it hatches.
From Seattle Times ● Mar. 31, 2024
"I mean, name another industry where 50 percent of the finished product immediately goes to the garbage can," said Jonathan Hoopes, president of Ovabrite, a Texas-based startup developing an in-ovo sexing technique.
From Salon ● Mar. 18, 2021
That might in part be because of more accurate ways of sexing skeletons.
From Slate ● Nov. 13, 2018
Turtle sexing is key for research purposes, and also for conservationists who are trying to pair mates.
From The Verge ● Jul. 29, 2017
Having discussed with my neighbour in the country the difficulty of sexing her ducklings, I now know, as Donne surely did, that sexing can be far from straightforward.
From "The Invention of Science" by David Wootton
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
