Interestingly, many scientists aren’t sure about this! Here’s a brief explanation of the difference between the two: according to the World Health Organization, “sex” refers to the biological and physiological characteristics that define men and women, and “gender” refers to the socially constructed roles, behaviors, activities, and attributes that a particular society considers appropriate for men and women. Thus, “sex” is a biological and physical variable, while “gender” is a social, cultural, and psychological variable. To be more specific, sex refers to the classification of living things—generally as male or female—on the basis of their reproductive organs and functions assigned by chromosomal complement, and “gender” refers to a person’s self-representation as male or female, or how that person is responded to by social institutions. Gender, though rooted in biology, is influenced by one’s environment and experience.
However, some scientists are not fully aware of this distinction or do not pay much attention to it. What’s more, certain feminist scholars tend to use the term “gender” in order to emphasize that most differences between men and women have a social and cultural basis, and other researchers feel that “gender” is more politically correct or less offensive than “sex” in scientific writing. In 2001, the Institute of Medicine of the National Academy of Sciences, United States, published a report strongly recommending that the usage of “sex” and “gender” be clarified.
It is important to pay attention to the correct usage of these terms, since incorrect usage might give readers the wrong idea of your research. Let’s look at an example of how these words can be misinterpreted. Researcher A studies malnutrition in country X and reports that the female sex is an important risk factor for malnutrition in Country X. From this wording, it seems that the women of that country have a genetic or biological predisposition to malnutrition. But in fact, what Researcher A wants to say is that Country X is a highly patriarchal society in which men eat first and women get to eat only the leftover food; this practice makes the women prone to malnutrition. If a woman from Country X migrates to a more egalitarian society where she gets to eat at the same time as the men in her family, she probably would not be at a greater risk of malnutrition than her male relatives are. In this case, female gender, not sex, would be the more appropriate term to use.
In short, it is important to understand the difference between “sex” and “gender” in academic writing, simply for the sake of more accurate reporting. I hope this explanation helps you.