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Sex vs. gender: What's the difference?

A photo illustration shows two teddy bears wearing stethoscopes in front of a sign proclaiming: It’s an XY!
Biological sex and gender identity expression, though largely interconnected, can sometimes hold different meanings for different people. (Illustration: Nathalie Cruz; photos: Getty)

Though the terms “sex” and “gender” are often used interchangeably, there are distinct differences between the two. Recognizing them, say experts, may help us better explain human identity and individual selfhood.

“Gender is important to everyone,” Charlotte Clymer, a transgender activist and former press secretary of the Human Rights Campaign, tells Yahoo Life. “As a concept, it’s the way we see ourselves, and our relationship to the world and to others.”

Still, “biological sex is not as easily defined as you might think,” adds neuroscientist Lise Eliot, executive chair of foundational sciences and humanities at the Chicago Medical School of Rosalind Franklin University and author of Pink Brain, Blue Brain, who says there are “many dimensions to sex and gender” that have existed “across human cultures.”

Having consistent definitions for these terms is vital for having clear communication about sex and gender in many aspects of life.

“‘Gender identity’ is a widely used term,” says Carole Hooven, an associate in the psychology department at Harvard University who recently served as co-director of undergraduate studies and lecturer on human evolutionary biology, and is the author of T: The Story of Testosterone, the Hormone That Dominates and Divides Us. “The way we define the term and understand the concept affects scientific research, health care policies, law, education, individual rights and so many other aspects of public and private life.”

Sex and gender: What are they?

Simply put, sex is the biological sex — female, male or intersex (displaying both male and female sex characteristics, accounting for roughly 1.7 percent of the global population) — that you are born into, or, as is becoming a widely used phrase, endorsed by groups from the American Psychiatric Association to the Human Rights Campaign, it is one’s “sex assigned at birth,” a phrase that acknowledges the belief that one’s sex is decided by someone else, such as a doctor.

Its classification is based on an array of factors “in most people,” explains Eliot: sex chromosomes (XX for female and XY for male), dominant hormones (estrogen for female, testosterone for males), reproductive organs (fallopian tubes and ovaries for females, testes for men) and related physical anatomy (a vulva and clitoris for females, a penis for males). However, various scientists have pointed out recently that these attributes aren’t always reliable determinants of one’s sex, which some argue is never “set in stone.” For example, there are people with testosterone or estrogen levels outside the typical “male” or “female” range, and people with XY or XX chromosomes born with ambiguous genitalia, due to the way certain genes were formed in the womb.

Adds Eliot, “Somewhere between 1 in 100 and 1 in 1,000 people have a range of phenotypes we call ‘intersex,’ where these chromosomal/gonadal/genital/hormonal traits don’t all line up in the typical way. So, that’s sex: mostly binary and all genetic in origin,” she says, “although the process of genital development is critically influenced by hormones, which themselves are ultimately shaped by genetic wiring.”

And once that “M” or “F” goes onto a birth certificate, it gets transferred to other forms of identification and has a direct influence on the roles and expectations people face in society.

Gender, on the other hand, is the social and psychological sense one carries of being male, female or any of the multitude of gender identities said to exist outside of the conventional definitions — including genderfluid (when one’s gender identity is not a fixed constant) or nonbinary (where one identifies as genderless), which is when some folks may use they/them pronouns. As described by the World Health Organization, gender refers to the “characteristics of women, men, girls and boys that are socially constructed.”

In Western society, gender has traditionally been viewed as a binary system consisting of two categories: masculine (boy or man) and feminine (girl or woman). These categories are shaped largely by the norms, behaviors and standards associated with being a man or a woman. Other societies, however, are known to have recognized multiple genders — such as the “Hijras” in India, what are known as “Two Spirit people” in Native American culture, the “muxes” in Mexico and the “bakla” in the Philippines.

“Gender is a human social invention. We have developed roles, pronouns and cultural norms for what a person with XX/ovaries/girl parts is expected to feel and behave like, which we teach from birth,” Eliot tells Yahoo Life. “It’s a lot like language, which is also learned from birth, and is fluent by the time a child is 3 years of age.”

Still, Hooven points out that we have a long way to go before sex and gender are seen as completely different.

“Overall I think ‘gender identity’ is a confusing term,” she says. “In some cases, it is just a substitute for the word ‘sex,’ as in, male or female, like when we talk about the ‘gender pay gap.’ Sometimes it’s used to mean masculinity and femininity. Sometimes ‘gender’ means social rules or norms about how women and girls, or boys or men, should behave. And sometimes ‘gender’ is simply an abbreviation for ‘gender identity.’

“I’d prefer we use more specific and descriptive terms [such as ‘sex roles’ instead of ‘gender roles’] that describe sex-based cultural norms and our comfort with them, masculine and feminine behavior and feelings, and biological sex,” she adds.

Sex and gender aren’t mutually exclusive

While biological sex is generally seen as fixed (though not always, as noted above), gender identity and gender expression (how a person expresses their gender through appearance, dress and behavior) is very often fluid. That means an individual’s perceived gender, and the expression of that gender, can change over the course of their lifetime.

For example, someone who was biologically born male may very well identify as a woman later in life, just as someone biologically born female may later identify as a man. This is called transgender, and is the experience of 5% of young American adults today, according to a 2022 Pew Research poll.

According to some research, feelings of gender dysphoria can begin as early as 3 years old. And for many trans people, coming to the conclusion that their gender identity doesn’t match their biological sex is a drawn-out, painful experience.

It often results in the diagnosis of gender dysphoria, which, according to the American Psychiatric Association, is given to transgender people experiencing “psychological distress that results from an incongruence between one’s sex assigned at birth,” based on external genitalia, “and one’s gender identity,” or the psychological sense of one’s gender.

Scientists like Hooven, however, argue that while gender dysphoria “has lots to do with biology,” at its core, the psychological distress gender dysphoria brings to a person has more to do with the discomfort they feel about social expectations that are associated with their biological sex (for example, playing with “girl” or “boy” toys, or wearing “girl” or “boy” clothes).

Clymer, a transgender woman, says that one’s transition journey is personal and unique to every individual, and that every experience should be “believed” and “taken as the truth, every time.”

Because of the psychological distress of gender dysphoria, many transgender people undergo gender-affirming care — credited by many trans adults as being a vital step toward living a full and happy life — which has been supported by leading health care organizations such as the American Psychiatric Association, the American Nurses Association and the World Medical Association.

Still, gender-affirming care remains controversial, especially for trans youth — not only in the U.S., where in 2023 alone, conservative state lawmakers have introduced over a dozen bills blocking minors from receiving gender-affirming care, but also throughout Europe, where several countries have taken steps to restrict access to gender-affirming care for minors.

Meanwhile, Shannon Minter, legal director of the National Center for Lesbian Rights and a transgender man, believes that “gender identity is a part of sex.” He tells Yahoo Life, “It’s just as biological as any other attribute of sex, and, from a legal point of view, it’s devastating to make that distinction because we are trying to get courts to say that sex discrimination laws protect transgender people.

“You get into these very complicated terminologies about: What is sex? What is gender identity? What is gender expression? ... It’s about people. We’re not in science class,” he says, adding that it’s mostly important to focus on humanity as opposed to terminology, and to be patient and “believe” people when they say how they identify, and to not use such discussions to make political points.

“Language is important,” he adds, “but what’s most important is just understanding and acceptance and inclusion and support.”

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