A handy dandy informational post clearing up common misconceptions on Gender, sex, and orientation (As modelled by the lovely deity Hermaphroditus)
A) Gender Identity is the one most often confused with sex. Sex is usually what you are thinking of when you think ‘gender’ but is more oft than not the wrong definition- see part C for further explanation of sex. Gender Identity is a lot more complicated and involves a number of things; primarily when looking at gender we look at cultural constructs and social ideas. Most people can name two; male and female. There is more than this however, a third gender in most societies -such as the Indian hijra or Samoan fa’afafine- and as many as ten in some cultures.
There are a lot of overlaps, as there are no official definitions of any genders and they are all defined individually by medical, psychological, and anthropological communities, and by gendered communities themselves.We do however have two main (In western societies, I can’t speak for any others) categories. That being Cisgender, a term for someone who’s gender matches their sex, and Transgender, an umbrella term for someone who’s gender does not match their sex. Some examples of transgender identities are transgender, pansgender and androgyne.
B) Sexual Orientation is not determined by gender (But more on that later). Sexual orientation is determined by the romantic and/or sexual feelings you may have towards other people. Again, the subject is not greatly researched which can lead to overlaps and slightly different definitions- but this doesn’t matter, because you don’t need someone else to define your sexual orienation, just like you don’t need someone to define your gender!
A couple of the more commonly recognised sexual orientations are:
- Hetrosexual- Attraction to the opposite sex
- Homosexual- Attraction to the same sex
- Bisexual- Attraction to both sexes
- Asexual- lack or near lack of sexual feelings (can still have romantic relationships and also identify as any of the other sexualities mentioned)
- Pansexual-A sexual attraction regardless of sex/gender
There are many more, as well as subcategories that I have not included for the sake of time, but you get the idea. Lastly, back to the ‘not determined by gender’ idea- by this I mean that a crossdressing male (sex) is not necessarily transgender, or even non-hetorosexual. Similarly, a transgender female (sex) does not necessarily have a sexual attraction to the same sex. Aaand so on.
C) Sex has a two definitions as I understand it. There’s ‘coitus’, as in what you do with your partner(s), and then there is the sex defined by your genitalia.This is what most people are thinking of if they think of gender. There are three different types.
Male:

Female:

Intersex:
This category has a range of natural variations handily illustrated and explained over at The Intersex Roadshow, which I’d put here but would make this post far too long. I do reccomend you check it out. Noteably, the deity Hermaphroditus was sometimes considered to be intersex, however more oft than not he was depicted as having a female body with male genitalia. (Pointless but interesting)
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And that, I believe, is all (*kind of) I have to say on the subject. I hope this is informative and helpful. [Note: Some information gained from here and here.]