Wikipedia: Sex/Talk

There is an increasing awareness that the two sexes are not discrete, but rather a continuum...

Some mention should be made of how this relates to the biological sexes as defined by role in reproduction and more generally by chromosomes (Y = male), which are very definitely discrete if not binary.

: Yeah. The above sentence sounds like cultural theorist tripe. Maybe gender is a continuum, but sexes aren't. --Robert Merkel

There are other sex chromosomes other than XX and XY, including XXX, XXY, etc. There are also some individuals who are mosaics -- i.e. some of their body cells are of one chromosomal sex, while others are of another. So chromosomal sex isn't a discrete dichotomy. -- SJK

The Y chromosome is dominant, so XXY counts as male while X and XXX count as female, at least with regards to the bulk of the anatomy, but I was already thinking of these when I said discrete if not binary. Mosaics are harder to categorize but they are pretty much inherently a mix of the two sexes, rather than a third sex separate from both (noone describes the truly hermaphroditic worms as having non-male-non-female sex). In any case, I think the distribution is sufficiently bimodal that emphasizing the continuity over the discreteness is a mistake. Evidently some people disagree, and in the spirit of NPOV I'm all for including what they have to say, but I'd include more details.

Also, IIRC some people have a different anatomical sex to their chromosomal sex, due to excessive levels of hormones in utero. If someone has male anatomy, but XX chromosomes, or vice versa, what then should we classify them as?

There is not one defintion of sex, but many -- chromosomal sex, internal anatomical sex, external anatomical sex, gender identity, social sex role, legal sex -- and although these different defintions most commonly coincide, they need not, and often don't. -- SJK

: In animals, sex is determined by a special sex chromosomes, whose alleles are called X and Y. Males typically have one of each, while females typically have two X chromosomes.

No way. For example in insects there are at least these systems: male XX/female XY, male XY/female XX, male X/female XX, male XX/female X and male haploid/female diploid. (X and Y are arbitrary sexual chromosomes, some of these combinations more frequent than others) There are more problems, because for many animals, sex is determined hormonally, not genetically, and can even change during adult live time.

: Typically means for the majority of forms, and it is true for the majority of forms. Others are special cases and deserve to be treated as special cases, and barring the male XX/female X, they are already covered by the text on the page. Can you give an example of this last category? I've never heard of any such insect. Anyways, if hormonal determination is more important, go ahead and add more stuff on it, as I'm not qualified. This is my main complaint: the page insists on continuity and various people here on cutting up the various forms of sex, but nowhere are there relationships to one another explained. It's like creating a page saying the Latin alphabet does not have 26 letters. Fine, and...?

Witness crocodiles -- their sex is determined by the temperature at which the eggs are incubated. So doesn't look like their sex is determined by their chromosomes.

In humans at least, it is not the chromosomes, but the presence or abscence of genes for the production of testis-determining factor and mullerian inhibiting factor which determine sex. These genes are normally found on the Y chromosome, but sometimes they are damaged or absent. In which case you get a woman with XY chromosomes. -- SJK