By way of John Scalzi’s Delicious bookmarks page, a thoughtful explanation of what people mean by ‘gender’ and why it is different from ‘sex’:
I have been asked at various times what people mean by “gender” and why it is different from “sex’. Also I’ve been asked to explain the multitudinous types of “trans” people, and why they often seen to be at each other’s throats. Hopefully I can traverse the various minefields involved without offending too many people, but sadly there are so many different perspectives out there that I’m bound to offend someone. My apologies in advance.
So, gender, what is it? Many people still think that gender and sex are the same thing. People, animals, even objects in many languages, are either male or female, one or the other, a very simple binary choice. Sadly life is never that simple. I’d like you to consider four different ways in which things are viewed as masculine or feminine.
Biological sex
That’s easy, isn’t it? People have one sort of dangly bits or the other. You either have XX chromosomes or XY chromosomes. You either produce sperm or eggs. Simple.
Well, no. Biology is a fickle thing. Many people are born with ambiguous biology. I don’t just mean genuine hermaphrodites, though such people do exist. All sorts of things can happen to us in the womb, and thereafter, that make our gender difficult to determine by physical tests. These conditions are known as “intersex”, and there are an enormous number of different ones. The Intersex Society of North America has a fairly comprehensive list of them together with data on how common they are. It is reasonably certain that as many as 1 in 1000 people have an ambiguous biological sex in one way or another, and as people get old and parts of their body wear out that can increase significantly.