+1 for "If you don't need to ask for a gender [or any other thing in your form] then don't."

This question is asking for sex, not gender. I assume the OP wants to avoid the word sex in the prompt, though, because it seems a bit awkward.

@Kylos Do you mean biological sex by birth, biological sex by correction or psychological sex? As I said in my answer, there's no need to ask anyone what private parts they have (or want) unless it's for medicine or health insurance

@AndrewMartin "Psychological sex" doesn't exist. Sex is always biological, determined by what you were born as and whether you have a Y chromosome or not. Everything else goes under the gender umbrella.

@Pryitie, So why would the system need to know that? And how does that counter for X0s and XXYs?

@Pyritie Be careful or you're riding a bulldozer on thin ice.

@AndrewMartin Any deviation from XX or XY are male or female chromosomal abnormalities, they aren't "new" genders.

@HenryA. That is true but that was in response to a comment about reducing it to just XX and XY - I was simply pointing out that those aren't the only two possibilities And, again, why would the survey want to know that?

@Pyritie there are at several misconceptions in your statement. Pease take it to biology.se for elucidation. You are mixing genital configuration (phenotype) with the genes behind them (genotype) in a discussion that is about gender. In broad XXI century.

@AndrewMartin You can't "correct" biological sex, unless someone has invented a procedure to add or remove the Y chromosome from human DNA.

@kylos the question is asking for gender. "male or female". Unless OP really wants to know the shape of the user's genitals, the question is about gender.

@Mindwin That has nothing to do with my comment. Neither of those things are called "psychological sex". "It's current year!" is also not an argument.

@Mindwin, male/female are sex, man/woman are gender.

@kylos-pyrite you both are getting lost in wordplay, and missing the point altogether.

@Mindwin why do you think gender is significant while sex is not? It's not just wordplay, one is a psychological construct, the other is fact. And that's not minimizing psychology, just recognizing that fact is not a necessary aspect of it.

@Kylos: There are not that many cases where the shape of someone's genitals is an important fact.

What's inside my head is interpretation, not fact. Language works best when it keeps to the facts, not interpretations. Your interpretation of the same facts will be different from mine. Communication is most clear when word definitions are tied closely to fact.

@cHao, I can think of several. :)

English uses gendered pronouns. Maybe it would be better to have no gendered pronouns at all, but we do. As it is, it is much simpler to treat our pronouns as sexed pronouns rather than gendered pronouns to avoid the need to create a potentially limitless number pronouns to describe every individual's gender expression.

@Kylos: But our pronouns aren't sexed, they're gendered. Who was it who wanted so much to bring facts into this? :) As far as genders go, we already have a line drawn: at the three that already exist -- masculine, feminine, and neuter -- plus possibly the singular "they" for unspecified/other. Anything past that would require top-down control of the language, and thus will likely never happen to a degree worth considering.

Good answer still think that some users will (sadly) not understand (or try to) the reason behind the order of the 2 genders, maybe alphabetic order would be better as it is easier to understand why that the genders are ordered alphabetically. as @Dmitry Grigoryev suggested.

@wannabeLearner: Two items isn't enough for a user to pick up on the ordering. It's going to look like an arbitrary decision either way. But if the order sounds awkward, it may well call itself out and look like a preference for one over the other.

@cHao I disagree, it may not be instantaneously but the person who takes 2 seconds to think about it will pick it up pretty quickly. Still it is a valid thought.

@wannabeLearner: Part of the point of UX design is to avoid that 2 seconds wherever you can.

@cHao still to some people this is important enough to spend 2 seconds, part of the point of UX design is to account for that.

@Pyritie you are full stop wrong. for 99+% of people you are correct, but there are people who genuinely (and rightly) identify with a gender different to their birth gender - the transgender community, and to say they don't exist is simply incorrect

@Cursed1701 Read my comment again. Transgender even has gender in its name! Sex and gender are different concepts and "psychological sex" is just muddied nonsense.