The Iranian fundamentalist regime, for example, is willing to pay for sexual reassignment surgery because it sees the existence of gay men and lesbians as the greater threat to the patriarchal contract. Everyone has the right to live as they wish in security and dignity and without fear of discrimination and stigma, but this cannot be achieved by hitching feminism or indeed other social justice movements to regressive ideological projects.

But the answer to the question “what is a woman?” is—like the answer to “what is a ewe?”—an almost mundane description of age, sex and species, albeit one with human significance in life and law, sport and data, and single-sex spaces and services. Just as a “ewe” is an adult female sheep, a “woman” is an adult female human.

Maybe asking “what is a woman” is an impossible question because there are any number of ways of being a woman.Perhaps all I can say is what makes someone a woman is simply a piece of unique, amorphous self-identity floating around in one’s brain, saying: “you are a woman.” Or, to put it more succinctly, paraphrasing an established principle from the trans rights movement: womanhood is what’s inside your head, between your ears.

These all strike me as different ways of responding to the coerciveness of our current gender order. While the ones that involve changing one’s gender or transforming one’s body throw up sometimes taxing problems regarding access to women-only services or how much prior counselling is appropriate before embarking on possibly irreversible change, I cannot see any one of them as more legitimate than any other. The body matters, shaping how others see us and how we see ourselves. Most of us will change something about our bodies in the process of changing ourselves—but the body is not destiny.

I believe that what defines a woman is her biological sex. The binary biological categories of male and female are a material reality even if there are variations of sexual development in-between. Throughout the world and throughout history, women have been and are subject to systematic subjugation on the basis of their sex; a subjugation that is legitimised through patriarchal power embedded in the institutions of the state, community and family. In many cultures, a woman’s destiny is mapped out the day she is born and, in some cases, while still in the womb.

Pragna Patel, former director of Southall Black Sisters

We know it means something different for Caitlyn Jenner, Kimberlé Crenshaw, JK Rowling, Cara Delevingne, James Charles, Beyoncé, Pope Francis, Lia Thomas, the Queen, Malala Yousafzai, an incel, Phoebe Waller-Bridge, Miriam Margolyes, or a man who buys a “non-bio woman” (an AI-enhanced sex doll which may cost up to $25,000 depending on which distinguishing features you choose).New senses of the word “ have appeared over time: woman as wife or a form of address (13th cent.), woman as a sexual partner or in contrast to a “lady” (15th cent.), woman as the embodiment of femininity (17th cent).

Nor are they to be confused with men who are not genuinely trans but who pretend to live as women in order to gain access to women’s spaces for ulterior reasons. I do not know how common this is and I understand how deeply concerned some women, especially those who have suffered abuse at the hands of men, are about that risk. It is, quite simply, bad behaviour and should not be tolerated. The difficulty lies in knowing which is which.

Like other animals that give birth to live young, female humans also provide their developing baby a safe space in which to grow during gestation.To describe as “female” a ewe that (just like a woman) has ovaries, a uterus and a vagina, who (just like a woman) produces eggs and gives birth does not attract handwringing analysis of what “ewe” means and whether some rams might be counted as one. It is a peculiarly human and almost religious practice to distinguish our own species from the rest of the animal kingdom, in this case with regards to sex.

I am a lawyer, and in law there are two sorts of woman: a person who was born a woman and has not transitioned to become a man under the Gender Recognition Act 2004; and a person who was born a man and has transitioned to become a woman under the same Act. But in practice there are people who were born either a woman or a man and experience gender dysphoria but have not yet completed the legal transition to the other gender. The current law requires them to live in the other gender for two years before their transition can be recognised in law.

Brenda Hale, former president of the Supreme Court

New spellings of woman have also emerged, some of them naturally occurring (Old English wifmann, Middle English wuman); others, especially in the 1970s, constructed to reflect a political stance (wimmin, womyn, womxn).Our definition of woman is not fixed. Language reflects culture, and culture changes over time. What is derogatory and offensive now won’t be to future generations. Some artists and activists try to force that change.

There are other people who are driven to live in the other gender, even if they do not intend to complete a legal transition. For practical purposes, people who live as women in this way are women.Genuinely trans people are among the most vulnerable and marginalised of groups in our society and deserve our understanding and support. They are not to be confused with men who like dressing up as women, any more than people who live as men are to be confused with women who like dressing up as men.

Much of society has deemed that a human becomes an “adult” during late adolescence.So it is “female” that is the source of controversy. Yet in biology and medicine, in the hundreds of thousands of textbook references and papers, it is no more controversial than “human” or “adult.” Almost all animals reproduce sexually, via the fertilisation of an egg by a sperm, and 95 per cent of animal species—including all mammals and birds—are divided into two reproductive classes of individual who, in the absence of illness, injury or disease, produce either eggs (females) or sperm (males).

To those who argue that sex is not a biological but a cultural and social construct, I would say that this cannot wholly explain why women and girls are the targets of many forms of harm throughout their lives: female foeticide (sex-selective abortion), female infanticide, FGM and reproductive coercion are just some of the harms that are perpetrated against women and girls on the basis of their biological sex. Feminists across the world have challenged these and many other abuses in the struggle for the right to female autonomy, including bodily autonomy.

Is being a woman a matter of biology, a product of an inner identity—or something in-between? A range of women, including a former Supreme Court judge, a biologist, an anthropologist, a linguist and a feminist campaigner give us their verdicts.

What is a woman?

What is a woman? What makes someone a woman? I should know. Shouldn’t I? I’m a cisgender, straight woman.My birth certificate says “female.” Is that what makes me a woman? No, it’s not that simple. A six-letter word—female—on a birth certificate or any other official document does not always determine womanhood.My reproductive organs played a large part in gifting me two children, and my breasts serviced them for months on end. But reproductive organs, menstruation, pregnancy, menopause, breasts and breast-feeding don’t always define womanhood or make one a woman.

Dawn Starin, anthropologist

For the most part, social and political institutions divide their populations into females and males. I easily fall into the female category in this gender binary system. Yet this system is not universal. There are many other ways we humans have organised genders; both in the past and present, three or more genders have been seen as a very natural way of being and being identified. Historically, people have often transcended binary ideas of gender. In India, the history of the Hijras, a third gender community, stretches back to ancient times.

Some terms for woman have been positive and heroic (virago, Zamazim, Amazon); ­others decidedly pejorative (strumpet, wench, malkin); some have died out (unchaghe, mot, kittock); others die hard (hussy, minx, skirt).Slang terms for a woman outnumber slang terms for anything else, more even than crime, alcohol, sex or race, and certainly men. Green’s Dictionary of Slang has 10,000 terms for a woman and thousands more referring to female body parts (1,500 words alone for vagina but only 27 for ­clitoris—clearly a woman’s pleasure is not a priority in slang).

People raise objections. The bathroom issue. Come, come, I go to the loo to pee. What do you do? The sports debate. ­Alright, let’s be reasonable and ­polite, and not have XY people with massive male muscles compete against XX people. I don’t know: maybe a test of muscle mass? Yet some of the XX people have a lot of that.Whether Ukraine is essentially Russian is a big issue. Whether people are essentially free adults is still bigger. Whether I am essentially a woman is not.

Since pre-Hispanic times in southern Mexico, there have been three ­recognised genders: muxes, females and males. Today, muxes are accepted and celebrated within their indigenous Zapotec community.Official documents, officialdom, sexual and reproductive organs, biology, external rules, laws, society and body parts (except for the one big one, the brain) cannot always automatically define one’s personal gender. Gender and therefore womanhood are probably determined by the self. And, just as there are no two identical women, there are no two usable identical definitions of womanhood.

Babies are identified as male or female on the basis of their genitals—though in a small number of cases the observations are inconclusive—and are then set off on the long process of acculturation into their assigned categories, learning the appropriate ways of holding their bodies, engaging in the world and envisaging their futures. Some of us accept the label, but resist the baggage attached to it, and try to practise a different version of what it is to be a woman.

It is uncontroversial to name an adult female sheep a “ewe” or to know that our scrambled eggs come from “hens.” Humans have long used nouns that denote individual animals by their species and sex (and often stage of maturity), including in relation to our own species: a “woman” is an adult female ­human.The least controversial of this triplet is “human.” Nobody disputes that the word “woman” applies uniquely to humans. And (almost) equally uncontroversially, “adult” denotes an individual who is fully developed and no longer dependent on others.

Emma Hilton, developmental biologist, University of Manchester

In The Vagina Monologues, Eve Ensler repeats the word cunt over and over until it (nearly) loses its shock value. The designer Suzi Warren makes t-shirts reclaiming negative words for woman: Sandi Toksvig chose crone, Mary Beard chose witch, I chose blue-stocking. If only it were that easy.

In most cases, the question that troubles people is not what is a woman, but what is a “real” woman. "Real” women are defined very differently in different periods and places. It is one of the paradoxes of gender that we are so often told it is in our nature to be women, as if biology is indeed destiny, and yet an enormous amount of effort is put into getting us to conform to whatever is the current paradigm.Others find the labels so incompatible with their sense of themselves that they choose to live in a different gender, undergo surgical or hormonal interventions, or redefine themselves.

Anne Phillips, professor of political theory, London School of Economics

Practically no one I know has regretted the decision. “Ecstatic” would be a better description of their state of mind. On the other hand, prevent it and you get deeply unhappy people.Second, get the politics right. Take the high road. In a free society, people get to make harmless choices. We are not classified permanently at birth as barristers or ploughmen, barmaids or accountants. The freedom of which most of us approve requires equality of permission. No castes, please: we’re British.

First, get the science right. Most born women have XX chromosomes, men XY. Intersex individuals can have other combinations. In the US, it is estimated that 1.4m people—or around 0.6 per cent of the population—want to change in social role from male to female or from female to male, though all the political excitement is about males to females. A little girl who says “I’m a boy” from age three onwards, refusing to wear dresses, is probably going to be happier as a boy. If he changes his mind, he can transition back.

Deirdre McCloskey, professor of economics, history, English and communication at the University of Illinois

Women need single-sex spaces to make sense of their shared biological and social experiences and to stay safe from the harms that they face.To those who say that this view can make feminism a natural ally of the religious right, I say that fighting for sex-based rights must lead us into necessary contestations with the religious or far right. Today, these forces represent one of the greatest threats to women and girls as well as to people who are same-sex attracted, other sexual minorities and those deemed to be non-conforming.

A woman is someone who identifies as an adult female human being. The word is in flux so no wonder politicians, who want to be all things to all people, find it so tricky to define. Usually language evolves gradually. But “woman” is changing fast, helped by social media, meaning we can watch its morphing definitions in real time.