Kenneth G. Wilson (1923). The Columbia Guide to Standard American English. 1993.
sex, gender (nn.)
A once-useful distinction between these two words is now blurred: gender, once limited to grammatical uses, has become more and more a synonym for what was once the biological term, sex. The Oxford English Dictionary labels biological uses of gender as jocular, but some feminists have adopted gender as a preferred word for sex, possibly as a more general word, possibly as a euphemism, which may already have suggested itself to the overmodest. See also SEXIST LANGUAGE.