What is the difference between sex and gender?

Recently, the UK Supreme Court ruled that, in the context of the Equality Act 2010, the term “woman” shall refer to a biological woman rather than a transgender woman. But what does that all mean? And what is the difference between sex and gender?

In my writing (both in my blog and in my book), I use the terms “women” and “men.” However, with gender identity as an emerging political topic, I thought distinguishing between the concepts of “sex” and “gender” might be helpful. This article will not discuss the politics of transgender rights, such as unisex toilets or transgender athletes in the Olympics. Rather, the aim is to define and differentiate gender from sex, and why scientists might use more traditional definitions of the two.

The terms "sex" and "gender" are often used interchangeably, but they refer to different concepts that are important to understand, especially in discussions related to biology, identity, and society. Here’s how they’re different:

Sex: Biological attributes

“Sex” refers to the biological differences between males and females, including chromosomes, hormones, reproductive organs, and genitalia. It is a classification based on physical and physiological characteristics. Here’s a breakdown of what constitutes biological sex:

1. Chromosomes: Typically, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). There are exceptions, such as individuals with Turner syndrome (XO) or Klinefelter syndrome (XXY), which demonstrate that sex chromosomes can vary.

2. Hormones: Sex hormones like estrogen, progesterone, and testosterone play a significant role in sexual development and function. Females generally have higher levels of estrogen and progesterone, while males have higher levels of testosterone.

3. Reproductive organs: Females typically have ovaries, fallopian tubes, a uterus, and a vagina, while males typically have testes, seminal vesicles, a prostate gland, and a penis.

4. Secondary sexual characteristics: These are physical traits that develop during puberty, such as breast development in females and facial hair in males. 

Gender: Social and cultural roles

“Gender” refers to the roles, behaviors, activities, and expectations that societies and cultures consider appropriate for men, women, and other gender identities. Gender is not necessarily tied to one's biological sex; it is a social and psychological construct. Gender can encompass:

1. Gender identity: This is a held sense of being male, female, a blend of both, neither, or somewhere along the gender spectrum. It is how individuals perceive themselves and what they call themselves. For example, someone may be assigned female at birth but identify as male (transgender male) or non-binary (not exclusively male or female).

2. Gender roles: These are societal norms dictating what behaviors, interests, and activities are deemed appropriate for individuals based on their perceived gender. For instance, do you think that women or men are more nurturing? Do you think one or the other is more assertive? While we might consider our expectations as truth, gender roles vary significantly across different cultures and time periods. If you think only women wear skirts, consider the Scottish kilt or the Indian lungi.

3. Gender expression: This refers to how individuals present their gender to the outside world, through clothing, behavior, hairstyle, voice, and body language. Gender expression can be masculine, feminine, androgynous, or somewhere in between, and it may or may not align with an individual's gender identity or biological sex. Gender expression is fluid, often playful, and deeply shaped by social context (West & Zimmerman, 1987). 

4. Non-binary and genderqueer identities: Some people do not identify strictly as male or female. Non-binary and genderqueer are umbrella terms for gender identities that fall outside the binary of male and female. These identities highlight that gender is not limited to two categories but can be fluid and diverse.

A Venn diagram showing the characteristics of sex (hormones, chromosomes, physical anatomy) and gender (self-identity, cultural norms, personal expression)

Interaction between sex and gender

Although sex and gender are distinct concepts, they are often intertwined in social perceptions and experiences. For example, societal expectations of gender can influence how individuals experience their bodies and express their identities. Additionally, while sex is biologically determined, it is important to acknowledge that intersex individuals—those born with variations in sex characteristics—challenge the notion of binary biological sex.

Homogeneity in science is not anti-transgender

One last thing. An essential aspect of experimental science is trying to determine cause-and-effect. Does yoga cause a reduction in blood pressure? Does headstand cause neck problems?

To reduce the number of confounding variables affecting the cause-and-effect relationship, homogeneity is helpful. Homogeneity in a study means that all the subjects or samples are similar in relevant characteristics. This helps ensure that the results are due to the variables being tested, not differences between the subjects. When everything being studied is alike (e.g. all the participants are postmenopausal Japanese women in their 60s, or cis-gender male lumberjacks under 40 in Bavaria),  the results will probably be more accurate and reliable because there are fewer differences that might confuse the results.

Having a similar group also makes it easier for other scientists to repeat the study and get the same results, which helps prove that the findings are true. In short, keeping things similar helps scientists learn more clearly about how things work.

Conclusion

In summary, “sex” is a biological concept based on physical attributes, while “gender” is a social construct related to identity, roles, and behaviors. Understanding the distinction between these terms is crucial for discussions about identity, equality, and human rights, especially as our understanding of both concepts continues to evolve.

Whether you think transgender women should be allowed to compete in the Olympics with biological women or not, I think we can all agree that everyone, no matter how they express their sex or gender, deserves to be treated with kindness and respect.

References & further reading

1. American Psychological Association. (2015). Guidelines for psychological practice with transgender and gender nonconforming people. American Psychologist, 70(9), 832-864.

2. World Health Organization. (2023). Gender and health. Retrieved from https://www.who.int/health-topics/gender

3. Fausto-Sterling, A. (2000). Sexing the body: Gender politics and the construction of sexuality. Basic Books.