Sex and gender are terms that are so commonly confused that many of us don't even realize they describe two very different things. Part of the confusion comes from the fact that there are many different definitions of sex. Some might not see a need to even distinguish the two.
But there are good reasons to understand the difference between these terms. Not just intellectually, but each term describes something that impacts our lives in multiple ways. And when we think about sex and gender as the same thing, we miss out on so much of human experience, and we all lose out.
Nothing in life is ever really black and white, or clear cut. But in broad terms, we can distinguish sex from gender by describing sex as something that is biological, and gender as something that is social and cultural. Or we might say that sex refers to the body, our genitals and our chromosomes, while gender refers to the meaning we put on our bodies.
A person's sex refers to an assignment they are given at birth (and sometimes before birth). When a child is born, or when a fetus is viewed by an ultrasound, a medical professional will usually say "it's a boy" or "it's a girl." Even though there are more than two ways that sex is expressed (biologically and genetically), the medical profession still insists on slotting all of us in one of two categories. This narrow way of defining sex may change over time, where people whose bodies and chromosomes don't meet expectations won't be assumed to be damaged or broken.
A person's gender refers to the way they think and feel about themselves, and the ways they act in the world that are masculine and feminine. Gender also refers to all the social stereotypes and expectations we have about what it means to act in masculine and feminine ways. Just like with sex, when it comes to gender, there are many ways it is experienced and expressed. And yet when it is talked about, it's often either or binary. With gender, we are already seeing greater acknowledgement of more than two genders, thanks in large part to trans activists.
You may already understand the difference between sex and gender. If you don't, and if you feel as if the difference is academic or splitting hairs, consider this question: thinking about your own life and the people you know, and considering the social expectations of what it means to be or act like a man or a woman, would you say that people's gender always matches their sex assignment at birth? Does everyone you know with a penis actually act in the ways the society expects a man to act? Is every person you've met with a vulva a portrait of stereotypical femininity? If you're paying attention, the answer to these questions is probably "no." It might be simpler to say that having a penis makes you a man and having a vagina makes you a woman, but the truth is much more complicated.
The truth is that while sex and gender are related, they are different. And one doesn't necessarily follow from the other (any more so than it follows that all tall people will like playing basketball or that everyone who grows up in a hot climate will like the heat).
One thing that sex and gender do share is that both are presented in the world as an either/or choice, but neither are. None of us are stereotypes, and none of us, can ever fit into such narrow categories.
Read More:
World Health Organization: What Do We Mean By "Sex" and "Gender"?

