Gender Guide

Gender is one of the most familiar features of everyday life and one of the most frequently misunderstood. This guide explains what gender is, how it differs from biological sex, how researchers and medical bodies define the core terms, and how the understanding of gender has evolved across history, law, and culture. It is written as a factual reference, not as advocacy or opinion.

What we mean by “gender”

In ordinary speech, “gender” and “sex” are often used interchangeably. In the fields that study the subject — psychology, medicine, sociology, and anthropology — they refer to related but different things. The American Psychological Association describes gender as the attitudes, feelings, behaviors, and roles that a given culture associates with a person’s sex, together with a person’s own internal sense of who they are. Gender is therefore partly social (the expectations a society attaches to being a man, a woman, or something else) and partly personal (an individual’s felt experience of themselves).

Because gender combines biology, psychology, and culture, no single discipline “owns” the definition. What most contemporary frameworks share is the recognition that gender is not reducible to a single trait. It has several components — the body a person is born with, the identity a person holds internally, and the way a person presents to the world — and these components do not always line up in the way a culture expects.

Sex and gender: related but distinct

Sex assigned at birth refers to the classification — usually “male” or “female” — recorded when a baby is born, typically based on external anatomy. Biological sex itself is a composite of several characteristics that usually align: chromosomes, gonads, hormones, internal reproductive structures, and external genitalia. For most people these characteristics point in the same direction, which is why a single label at birth is workable in the vast majority of cases.

They do not align for everyone. Intersex is an umbrella term for people born with reproductive or sexual anatomy that does not fit typical binary definitions of male or female — for example, differences in chromosomes, hormone response, or genital development. Intersex variations are a matter of physical biology and are distinct from gender identity; the existence of intersex traits is one reason biologists describe sex as a cluster of characteristics rather than a single switch.

Gender, by contrast, refers to the social and psychological dimension: the roles a culture assigns, and the internal sense a person has of their own gender. The distinction between sex and gender was popularized in the mid-twentieth century by researchers who needed language to describe cases where a person’s felt identity did not match the sex recorded at birth. The distinction is now standard in medicine and the social sciences, even as the precise boundaries remain a subject of ongoing scholarship.

Gender identity and gender expression

Two further terms do most of the work in modern discussions, and keeping them separate prevents a great deal of confusion.

Gender identity is a person’s deeply held, internal sense of their own gender — whether they experience themselves as a man, a woman, both, neither, or something else. It is not directly visible to others and is not the same as sexual orientation, which concerns who a person is attracted to. A person’s gender identity and their sexual orientation are independent: knowing one tells you nothing definite about the other.

Gender expression is the outward presentation of gender — clothing, grooming, mannerisms, voice, name, and pronouns. Expression is what other people actually observe, and the norms for it vary enormously across time and place. Trousers on women, long hair on men, and cosmetics on either were each controversial in some Western era and unremarkable in another. Expression can align with identity, or it can be constrained by circumstance, safety, or personal preference.

When a person’s gender identity matches the sex they were assigned at birth, the standard term is cisgender. When it does not, the umbrella term is transgender. These are descriptive categories, not the whole of anyone’s identity, and the Terminology guide defines them and the surrounding vocabulary in detail.

The range of identities

Historically, many Western societies treated gender as a strict binary: everyone was expected to be a man or a woman, with the two mapped directly onto sex assigned at birth. Contemporary frameworks still recognize that most people identify as men or women, but they also acknowledge identities that do not fit neatly into either box.

• Cisgender — identity aligns with sex assigned at birth.
• Transgender — identity differs from sex assigned at birth; an umbrella that includes many specific identities.
• Nonbinary — identity is not exclusively male or female; may combine elements of both, shift over time, or fall outside the binary entirely. Genderqueer is a closely related term.
• Agender — little or no felt sense of gender.

These categories are ways of describing experience, and the vocabulary continues to develop. Different communities and generations favor different words, which is one reason a reference library treats terminology as a living subject rather than a fixed list. What matters for understanding the debates covered in the Commentary section is simply that “man” and “woman” do not exhaust the ways people report experiencing gender.

Medical and psychological understanding

The way clinicians classify gender has shifted markedly over the last half-century, and the direction of that shift has been away from treating a transgender identity as, in itself, a mental disorder.

The American Psychiatric Association’s Diagnostic and Statistical Manual (DSM) first included a formal diagnosis related to gender in the third edition (DSM-III, 1980), which listed “transsexualism” and “gender identity disorder.” In 2013, the fifth edition (DSM-5) replaced these with gender dysphoria — a deliberate change of emphasis. The new term names the distress that can accompany a mismatch between identity and assigned sex, rather than labeling the identity itself as disordered. Under this framing, being transgender is not a mental illness; dysphoria, when present, is a treatable condition.

The World Health Organization made a parallel move. In its eleventh revision of the International Classification of Diseases (ICD-11, adopted 2019 and in effect from January 2022), it removed “gender incongruence” from the chapter on mental disorders and placed it in a chapter on sexual health — retaining a code that can support access to care while explicitly declassifying it as a mental illness.

Clinical care for adults who seek it is guided by standards published by the World Professional Association for Transgender Health (WPATH), whose Standards of Care date to 1979 and were most recently revised (version 8) in 2022. Care for minors is far more contested, both clinically and legally, and is discussed in the next section rather than resolved here.

Legal recognition and its limits

Legal recognition of gender in the United States is a patchwork that varies by jurisdiction and by document. The ability to change the name and gender marker on a birth certificate, driver’s license, or passport has expanded over the past several decades but remains inconsistent from state to state, and federal policy on documents such as passports has changed repeatedly with different administrations.

Two Supreme Court decisions anchor the recent legal landscape:

• Bostock v. Clayton County (June 15, 2020). By a 6–3 vote, with Justice Neil Gorsuch writing for the majority, the Court held that Title VII of the Civil Rights Act of 1964 — which bars employment discrimination “because of sex” — also bars discrimination based on sexual orientation and gender identity, reasoning that it is impossible to discriminate on those grounds without taking sex into account.
• United States v. Skrmetti (June 18, 2025). By a 6–3 vote, with Chief Justice John Roberts writing for the majority, the Court upheld a Tennessee law (SB1) restricting puberty blockers and hormone therapy for gender transition in minors. The majority concluded the law classifies on the basis of age and medical use rather than sex or transgender status, and so does not trigger heightened constitutional scrutiny; it was therefore reviewed under the more deferential rational-basis standard. The dissent argued the law does classify by sex and should have received heightened scrutiny.

Gender across cultures

The idea that gender comes in exactly two kinds is common but not universal. Many societies have long recognized social roles that sit outside a strict man–woman binary, and these traditions predate modern Western terminology by centuries.

• Two-Spirit is a contemporary umbrella term, adopted in 1990, for a range of gender and social roles recognized in various Indigenous North American cultures. It is specific to Native contexts and is not simply a synonym for “transgender.”
• Hijra communities in South Asia have a documented history stretching back centuries and hold a recognized legal status as a third gender in India, Bangladesh, and Pakistan.
• Fa’afafine in Samoa and comparable roles across Polynesia describe recognized social genders distinct from man and woman.
• Records from a number of other cultures — from the muxe of Oaxaca to historically documented roles in parts of the Middle East and East Asia — describe additional gender categories.

These examples do not all map neatly onto one another or onto modern Western identities, and it would be a mistake to flatten them into a single category. Their relevance to this library is narrower and factual: the binary familiar to many readers is one cultural arrangement among several that human societies have adopted.

Why language and framing matter

Debates about gender are often, at bottom, debates about words: what “woman” means, whether “sex” and “gender” can come apart, which terms are respectful and which are dated. Because the vocabulary is evolving and politically charged, the same word can carry different meanings for different speakers, and a good deal of apparent disagreement is really people talking past one another.

This library’s approach is to define terms as the major professional bodies define them, to note where usage is contested rather than to declare a winner, and to keep factual reference separate from opinion. Where you want argument and analysis — a point of view on how these questions should be resolved — that is the work of the Commentary section. Where you want the background — what the terms mean, where they came from, and what the law currently says — that is the purpose of these pages.

For the vocabulary in depth, see the Terminology guide. For how today’s debates took shape, see the History of gender politics.

Common misconceptions

A handful of recurring errors cause much of the confusion in public discussion. Naming them plainly is one of the most useful things a reference can do.

• “Sex and gender are the same thing.” In everyday speech they overlap, but the disciplines that study the subject treat sex assigned at birth (a bodily classification) and gender (a mix of social role and internal identity) as distinct, precisely because they do not always coincide.
• “Being transgender is a modern invention.” The modern vocabulary is recent, but gender-variant people and recognized non-binary social roles appear across many cultures and throughout the historical record, as the History section documents.
• “Gender identity is just a synonym for sexual orientation.” They are independent. Identity is about who a person is; orientation is about who a person is attracted to.
• “A transgender identity requires surgery or hormones.” Transition can be social, legal, or medical, and many transgender people pursue none of the medical steps. Identity does not depend on any procedure.
• “Recognizing more than two genders is unscientific.” Most people identify as men or women, and no framework disputes that. But biologists describe sex itself as a cluster of characteristics rather than a single switch, and anthropologists document societies that have long recognized additional social genders. The binary is one common arrangement, not the only one on record.

None of these clarifications settles the harder normative questions — how institutions should respond, where lines should be drawn, whose interests take priority. Those are the province of argument, not definition, and they belong to the Commentary section rather than here.

Frequently asked questions

Sources and further reading: American Psychological Association and American Psychiatric Association guidance on gender and gender dysphoria; World Health Organization ICD-11 (in effect 2022); World Professional Association for Transgender Health, Standards of Care v8 (2022); Bostock v. Clayton County, 590 U.S. 644 (2020); United States v. Skrmetti (2025).