I hear people say
he’s homosexual
he’s a homosexual
he’s queer
he’s a queer
It it correct to say “a gay”
as in He’s a gay
If you want to sound like my grandmother, sure go right ahead.
If you put the “a” before gay, gay becomes an adjective instead of a noun. “He is a gay man,” would be correct.
Gay already is an adjective instead of a noun, as in “he’s gay”, just like “he’s angry”, “he’s tall”, “he’s white”, etc.
If you call someone “a gay”, I suspect people will look at you funny, but not for linguistic reasons. “A gay” is insulting and (to me) sounds belittling, kind of like “one of those people”. Why is “a queer” not similarly insulting? Probably as a result of the LGBT community reclaiming that word. As for “a homosexual”, I can only speculate that it’s a more scientific-sounding term, but it probably sounds insulting from some people.
“Gay” as a noun is correct in Britain, if Daffyd Thomas is to be believed.
The correct term is “he’s got the gay.”
Yeah, we use the noun “gay” as a joke. Like when someone’s parents are coming to visit (we live in the Castro) and we’re worried they’ll be frightened by all “The Gays™.”
Lewis Black has a bit about gay marriage, and he always says “the gays,” and it makes me cringe every time. Sounds very fuddy-duddy-ish. Same with “the Blacks.”
To say “He’s a gay” is not only wrong, it’s considered offensive in some circles. I’m surprised you haven’t been pitted mercilessly by now. You should always use the definite article. “He has the gay.”
It’s a very common and normal process in English for adjectives to become nouns, so there is nothing odd about "gay"becoming a noun. Whether it’s insulting or not is another question – but there would be nothing intrinsically insulting about calling a person “a gay”.
Of course there’s nothing wrong with using it as a noun. It’s common enough in the plural form (“Gays as a percentage of the general population, etc”), it just sounds odd as a singular because it’s rarely used as such.
Correction, “teh gay.”
As a gay, I find the construction “a gay” to be foolish. A gay what? Same goes for “a queer” unless it’s being used as an insult.
I don’t think anyone would be offended per se (though of course, some people are offended by everything). The Gay™ in question would probably just think it sounded thilly. 
They did this joke on The Larry Sanders Show when utterly un-hip homophobe fuddy-duddy Hank refers to someone as ‘a gay’ Larry looks at him and says, “A gay?! What are you, Italian?” which is probably also offensive…
It just sounds wrong to my ears, the same way that “a black” sounds wrong, though both words when plural sound normal (blacks, gays.)
Sort of like we say “the English” but not “an English.”
(I, myself, prefer to identify as “t3h gh3yxx0rz.”)
Well, sometimes it works and sometimes it doesn’t. No one has any problem saying “an Indian”, though few would say “a Chinese”. I actually don’t see anything terribly unusual about using “black” or “white” as nouns in reference to people, but I’ve been excoriated for defending the construction on these boards before. Then again, I don’t find use of “gay” as a noun to be terribly jarring either (nor “lesbian”, which may be a more common noun). That having been said, it only works in specific ways for me. I couldn’t really say “John is a gay”; I’d have to say “John is gay”. But I could easily say “Gays have long been stereotypically associated with a lisp”, or some such thing. But I suspect I may be out of tune with the speech community at large here.
Right. There are some adjectives describing people that are homonymous with the associated noun (“Canadian”, for example, or “lesbian”) and others that aren’t (“British” or “gay”). You can still say “the British” or “gays” but you can’t say “a British”, and many people will avoid saying “a gay.”
I don’t think it’s especially offensive, just ungrammatical.
Saying that someone is “an Indian”, to me sounds like they’re specifically from America. Saying someone is “Indian” indicates that they’re from India.
That’s kind of interesting; I’ve never run across that before, but now that you mention it, I definitely do think “he’s Indian” is more strongly disambiguated towards India than “he’s an Indian”, although both come out primarily in reference to India for me. Anyway, if it helps the example, replace it with “a Russian” or whatever you like.
I don’t even own a gay, let alone many gays that would necessitate a rack.