Skip to Main Content

What Do We Mean By Sex and Gender?

September 19, 2021
by Carolyn M. Mazure

At Women’s Health Research at Yale, we are committed to advancing the health of a diverse society. We do this in large measure by studying the health of women and the similarities and differences in health outcomes between and among women and men. As we pursue our work, it is particularly important to use language that captures the different concepts of sex and gender so that our science and our findings can be more precise and better serve everyone.

What do we mean by sex and gender? Aren’t these terms interchangeable? Perhaps at some point in time they were used as synonyms, but this is no longer true in science.

In 2001, a committee convened by the Institute of Medicine (IOM), a nonprofit think tank that took on issues of importance to the national health, addressed the question of whether it mattered to study the biology of women as well as men.

The IOM, now embedded within the National Academies of Science, Engineering, and Medicine (NASEM), concluded there was more than sufficient evidence that, beyond reproductive biology, there were major differences in the biology of women and men that greatly affected their health and influenced treatment and prevention strategies.

Importantly, the committee emphasized that neither the health of women nor men is simply a product of biology but is also influenced by sociocultural and psychological experience. To differentiate between these broad areas of investigation, the members created working definitions of “sex” — when referring to biology — and “gender” — when referring to self-representation influenced by social, cultural, and personal experience.

The committee advised that scientists use these definitions in the following ways:

  • In the study of human subjects, the term sex should be used as a classification, generally as male or female, according to the reproductive organs and functions that derive from the chromosomal complement [generally XX for female and XY for male].
  • In the study of human subjects, the term gender should be used to refer to a person's self-representation as male or female, or how that person is responded to by social institutions on the basis of the individual's gender presentation.
  • In most studies of nonhuman animals, the term sex should be used.

These working definitions were a good start in recognizing the value of studying sex and gender and their interactions, yet they were always meant to evolve. Now, we are learning more about ourselves and so must adapt our terminology to be inclusive, respectful, and more accurate.

For example, while most people are born biologically female or male, rare biological syndromes can result in genital ambiguity. Or a resistance to a sex hormone can result in traits typical of the opposite biological sex.

Moreover, while an individual’s internal sense of gender can be female or male, some people identify as nonbinary — neither female nor male. Other individuals can identify as a gender that is the same as (cisgender) or different from (transgender) the one assigned at birth. These terms are separate from an individual’s sexual orientation, which describes a person’s emotional, romantic and/or physical attachments (such as straight, lesbian, gay, asexual, bisexual, and more).

In science, as our understanding grows, so must the precision of our language in communicating what we know.

Submitted by Rick Harrison on September 13, 2021