Is it offensive to refer to women as "females", as I've seen posted at the entrance of a night club:
"Females under the age of twenty-one will have to...."
Is it offensive to refer to women as "females", as I've seen posted at the entrance of a night club:
"Females under the age of twenty-one will have to...."
Although OED traces the usage of female as a noun even further back than its usage as an adjective, the adjectival usage has long been more prevalent. Partly for this reason, referring to a woman as a female tends to focus attention on just a single attribute, one that she shares with many other animals and even plants, at the expense of other attributes that she shares with other (male) members of her own species, such as the capacity for articulate speech.
Thus using a single attribute as a metonym or synecdoche for a person is inherently depersonalizing, so yes I would avoid it as likely to cause offense. Examples vary from the club sign’s calling women “females,” to a waiter’s referring to a diner, or a surgeon’s referring to a patient, by the name of the entrée or operation ordered.
No, it's not offensive at all to refer to women as females. Female is just a little more formal or clinical.
At night clubs in the United States (more or less depending on the type of clientele) female is an overtly polite substitute for bitch (which at some night clubs [again, depending on the clientele] is a neutral term for a woman of reproductive age), since many people consider bitch an impolite term. In the right kind of night club, calling a woman a female comes with the subtext of 'I am not going to use the word bitch because I am not ignorant like that.'
I think women is preferable, for the reasons given by @Brian - unless the sign is also aimed at female horses, guinea pigs, armadillos etc. Maybe the real issue here is: What will the women under 21 have to do? Do men under 21 have to do the same? If so, how are they referred to, as males or as men? And if not, why not?
To answer @Frank 's comment above (sorry to put it here but my comments won't load for some reason) - if female is 'the least likely' to offend out of 'women, ladies and girls', what non-offensive term is anyone supposed to use to the half of the human race that is not male?
If the night club means women under the age of 22, then it can say that: women under the age of 22. If, however, it means any female person under the age of 22 then females under the age of 22 is appropriate. (Here, females is presumed to mean female people and not, say, female goldfish.)
If you were to complete the message on the sign for us then we might be able to guess which is more appropriate. The "..." might be something that clearly applies only to women. Or it might be something that applies to a female person of any age.
In the first case, one might wonder what the night club considers to be the minimum age for a woman (18? 13? 20?), or what other qualification besides age it might use for that.
An alternative for the second case is to say women and girls under the age of 22.