People often use the terms “sex” and “gender” interchangeably, but this is incorrect. Sex and gender are different, and it is crucial to understand why.

“Sex” refers to the physical differences between people who are male, female, or intersex. A person typically has their sex assigned at birth based on physiological characteristics, including their genitalia and chromosome composition. This assigned sex is called a person’s “natal sex.”

Gender, on the other hand, involves how a person identifies. Unlike natal sex, gender is not made up of binary forms. Instead, gender is a broad spectrum. A person may identify at any point within this spectrum or outside of it entirely.

People may identify with genders that are different from their natal sex or with none at all. These identities may include transgender, nonbinary, or gender-neutral. There are many other ways in which a person may define their own gender.

Gender also exists as social constructs — as gender “roles” or “norms.” These are defined as the socially constructed roles, behaviors, and attributes that a society considers appropriate for men and women.

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Sex assignment typically happens at birth based on anatomical and physiological markers.

Male and female genitalia, both internal and external, are different, and male and female bodies have distinct hormonal and chromosomal makeups. Doctors use these factors to assign natal sex.

At birth, female-assigned people have higher levels of estrogen and progesterone, and while assigned males have higher levels of testosterone. Assigned females typically have two copies of the X chromosome, and assigned males have one X and one Y chromosome.

Society often sees maleness and femaleness as a biological binary. However, there are issues with this distinction. For instance, the chromosomal markers are not always clear-cut. Some male babies are born with two or three X chromosomes, just as some female babies are born with a Y chromosome.

Also, some babies are born with atypical genitalia due to a difference in sex development.

This type of difference was once called a “disorder of sex development,” but this term is problematic. In a 2015 survey, most respondents perceived the term negatively. A further review found that many people do not use it at all, and instead use “intersex.”

Being intersex can mean different things. For example, a person might have genitals or internal sex organs that fall outside of typical binary categories. Or, a person might have a different combination of chromosomes. Some people do not know that they are intersex until they reach puberty.

Biologists have started to discuss the idea that sex may be a spectrum. This is not a new concept but one that has taken time to come into the public consciousness. For example, the idea of sex as a spectrum was discussed in a 1993 article published by the New York Academy of Sciences.

In the United States, gender has historically been defined as a binary. Many other cultures have long recognized third genders or do not recognize a binary that matches the American understanding.

In any case, the idea of gender as an either/or issue is incorrect.

Someone who identifies with the gender that they were assigned at birth is called “cisgender.”

Someone who is not cisgender and does not identify within the gender binary — of man or woman, boy or girl — may identify as nonbinary, genderfluid, or genderqueer, among other identities.

A person whose gender identity is different from their natal sex might identify as transgender.

A 2016 review confirms that gender exists on a broad spectrum — in contrast to the genetic definitions of sex.

A person may fully or partially identify with existing gender roles. They may not identify with any gender roles at all. People who do not identify with existing gender binaries may identify as nonbinary. This umbrella term covers a range of identities, including genderfluid, bigender, and gender-neutral.

Gender and society

Gender is also a social construct. As the World Health Organization (WHO) explains:

“Gender refers to the socially constructed characteristics of women and men, such as norms, roles, and relationships of and between groups of women and men. It varies from society to society and can be changed.”

Gender roles in some societies are more rigid than in others. However, these are not always set in stone, and roles and stereotypes can shift over time. A 2018 meta-analysis of public opinion polls about gender stereotypes in the U.S. reflects this shift.

Gender and health

There are complex relationship between gender and both physical and mental health.

Health systems are not gender-neutral.

A WHO report highlights the ways that gender stereotypes and stigmas influence a person’s healthcare experience. Gender stereotypes can affect health coverage, pathways of care, and accountability and inclusivity within health systems throughout the world.

A review of first-hand case studies shows that by failing to address gender-based inequalities, health systems can reinforce prescriptive and exclusive gender binaries.

The researchers also emphasized that these inequalities in care can intersect with and amplify other social inequities.

The review concluded that health systems must be held accountable to address gender inequalities and restrictive gender norms.

A person may identify and express their gender in different ways.

Gender identity is how a person feels internally, while their expression is how they present themselves to the outside world. For example, a person may identify as nonbinary but present as a man to the outside world.

GLAAD, formerly called the Gay and Lesbian Alliance Against Defamation, describes gender identity as “one’s internal, personal sense” of belonging at some point on or off of the gender spectrum. The organization adds:

“Most people have a gender identity of man or woman (or boy or girl). For some people, their gender identity does not fit neatly into one of those two choices.”

GLAAD describes gender expression as: “External manifestations of gender, expressed through one’s name, pronouns, clothing, haircut, behavior, voice, or body characteristics. Society identifies these cues as masculine and feminine, although what is considered masculine and feminine changes over time and varies by culture.”

For centuries, many societies have enforced the notion that a person is either a man or woman based on their physical characteristics. This idea conflates sex and gender, which is incorrect. Sex and gender are not the same.

In general terms, sex refers to a person’s physical characteristics at birth, and gender encompasses a person’s identities, expressions, and societal roles.

A person may identify with a gender that is different from their natal sex or with no gender at all. The latter identity is often referred to as nonbinary, but this is an umbrella term that covers many identifications.