A common paraphrase of H.L. Mencken says: “For every complex question there is an answer that is clear, simple – and wrong.” These days we see how helpful that quote is, when it is applied to the question “What is a woman?”

The OED’s first definition of “woman” is “an adult female human being”. Webster says “an adult female person”. It has become a commonplace on the right, of late, to feel so very clever by defining “woman” as “adult human female” – roughly but not exactly following the dictionary definitions – and then watch others struggle to provide their own definition. UK activist Kellie-Jay Keen-Minshull put up billboards proclaiming as much; director Matt Walsh even made a whole movie with this definition as its thesis. The intended point of this exercise, of course, is to say that transgender women are not really women and that presumably this should be obvious. And while I do think it can reasonably be debated whether trans women are women, this particular piece of rhetoric does far more to illustrate foolishness on the anti-trans side than the pro-trans side.

The surest sign that someone hasn’t really thought about the meaning of a word is that they quote the dictionary as scripture. That is the notorious rookie mistake made by legions of undergraduate essay writers, who haven’t yet learned that definitions are themselves contested, and dictionaries aim only to reflect common usage over time. Thus the Cambridge Dictionary already includes a definition of “woman” as “an adult who lives and identifies as female though they may have been said to have a different sex at birth.”

Dictionary or no, even the definition of “woman” as “adult human female” only sounds simple. Because none of those three words are simple in turn. Let’s take them in order.

Start with “adult”, which is presumably in the definition to distinguish a “woman” from a “girl” (leaving aside the fact that the term “girl” is applied to adults all the time). But what counts as an “adult” is different from society to society, and even within societies. Mexican quinceañera celebrations are held to mark adulthood – at 15. The “age of majority” in the US is 16 for driving, 18 for voting, 21 for drinking. Is an American 19-year-old a girl in a bar but a woman in the voting booth? Does she become a woman by virtue of entering a British bar?

This isn’t to argue against the different ages that constitute adulthood, only to say what should be obvious: that the concept of adulthood isn’t simple, and therefore a definition of “woman” as “adult human female” isn’t either.

Turn next to “human” – a term which isn’t actually in Webster’s definition. And rightly so, because as Marcus Arvan and Amos Wollen point out, we speak of nonhuman women all the time in contexts of fantasy and science fiction. Long before the trans movement, nobody batted an eyelash at the mention of elven women or Klingon women. If one is going on plain speech and preexisting common usage, it’s clear that these fictional characters are women, while explicitly being identified as nonhuman.

As for “female”: given the stock that the anti-complexity right puts in dictionaries, it’s of major importance that Webster itself has added a definition of “female” as “having a gender identity that is the opposite of male” (emphasis added); Oxford, too, following the definition of “designating the sex which may bear offspring”, has added the meaning “designating the gender or (in later use) gender identity associated with this sex”. As they should – because, as mentioned, dictionaries reflect common usage, and like it or not, these new meanings are now in common usage.

And of course, if one defines “female” in that way, then the “adult human female” definition itself becomes trans-inclusive in exactly the way the definition was deployed to avoid. You probably shouldn’t play the dictionary definition card when the dictionaries themselves are going to change their definition to the one you oppose. Simplistic thinkers like Walsh and Keen-Minshull have, to use a term current when their preferred definitions were still the main ones in the dictionary, been pwned.

But even before the recent additions of these new dictionary definitions of “female”, the definition was still contested – yes, even in scientific contexts. An article in Cell by Beans Velocci points out that the scientific meanings of “female” and “male” have changed significantly over time. The oldest usage defined them in terms of external anatomy, a penis or vulva, and this is still the way medical doctors most commonly assign the sex of human fetuses or newborns. But this practice is already at odds with the most commonly accepted scientific definition, based on the size of internal gametes (small gametes, such as sperm in humans, are male; large ones, such as ova, are female). The gamete-size definition was generally adopted primarily because it was thought to apply consistently across all eukaryote species, but Ottawa biologists led by Root Gorelick pointed out that it actually doesn’t; in several species of plants, for example, the varieties identified as “male” and “female” actually have similar gamete sizes to each other. And so, they add, “currently, there are no universal criteria for distinguishing females from males across all animals, across all plants or across all stramenopiles, let alone across all eukaryotes.” And of course there is a long-acknowledged presence of intersex organisms, what were once called hermaphrodites, in many species: organisms whose supposed sexual characteristics, especially chromosomes, do not line up neatly in the way they’re expected to. Thus a recent article in Cell, by Madeleine Pape with many collaborators, points out that even in scientific contexts, definitions of sex need to be context-specific.

Returning to the far less scientific claims of Walsh and Keen-Minshull, I notice they don’t make signs or movies about the dictionary definition of man. One reason for this, I suspect, is that that would itself require admitting more complexity. After all, even when I was growing up in the ’80s, the term “man” was regularly used to refer to “humanity” of both sexes or genders, in a way that was supposedly gender-inclusive, and I imagine is still used that way in a few quarters. Anthropologists used to claim the central question of their field was “What is man?”, and took it for granted that women counted as part of man. On the standard linguistic usage of the 20th century, a woman is a man, in a key sense of that term. Most of us now view that sort of usage as sexist, and I think rightly so – yet in the present context, it reminds us that defining “man” was never even as simple as “adult human male” claims to be.

Okay, so what is a woman? I hope by now it’s clear that the only appropriate short answer, to this as to so many other questions, is “it’s complicated”. That’s true even if one leaves trans people entirely out of consideration, and it’s even more true now that we have become socially accepted enough that a definition acknowledging us has made it into the dictionary. Words and concepts have long histories and shades of meaning around them that add subtle connotations and nuances beyond first appearance. “It’s complicated” is never the end of the story – that’s the point – but it’s the right beginning. You should be suspicious of anyone who rejects “it’s complicated” as the short answer to any question.

The anti-trans right has no monopoly on such oversimplified thinking, of course. The Nation writer David Klion, in a notorious and now-deleted tweet, proclaimed that “It’s incredible how many years I wasted associating complexity and ambiguity with intelligence. Turns out the right answer is usually pretty simple, and complexity and ambiguity are how terrible people live with themselves.” Walsh and Keen-Minshull are operating closely in line with Klion’s slogan: they all believe the world is better if we stop thinking and reduce everything to simple brute slogans that allow our side to win. Slogans like “a woman is an adult human female” are designed to function exactly like “four legs good, two legs bad”: the point is to shut thought down and make us dumber, for the purpose of the sort of oversimplified political agenda that withers under serious scrutiny. Don’t give that win to the advocates of stupidity – on either side.

I’ll be travelling the next two weeks and taking a break from weekly posting. Love of All Wisdom will return on 26 October.

EDIT (6 Oct 2025): I originally listed the OED’s first definition of “woman” as “an adult human being”, a typo which makes no sense. Corrected to the actual first definition as I’d intended: “an adult female human being.”