In which I try to explain why "guys" doesn't necessarily refer to a group of men in English.
"You guys" is the gender-neutral second-person plural pronoun in many English dialects, especially the western US and Canada. It's equivalent to "you all," "y'all," "youse," "you lot," etc.
If your dialect uses "you guys" as the second-person plural, try to avoid it online, or use "y'all"/ "you all" instead. You might sound like you're from the South, but at least nobody will feel confused or excluded.
I was born in the US Midwest, raised in Seattle, and briefly lived in Ontario. In all three places, "you guys" was the gender-neutral second-person plural, analogous to "vous" in French, "vosotros" in Castlian Spanish, "Sie" in German, etc. (Although it lacks the formal connotation.)
In my dialect, "you guys" has very little relation to the word "guy," and it applies equally well to a group of women as to a group of men, or to a mixed group. There's no confusion about this for native speakers.
For instance, Alice could ask Barbara and Carol:
"Are you guys coming to the party?"
And it's immediately obvious that she's asking whether both Barbara and Carol are coming.
Conversely, if Alice had said:
"Are you coming to the party?"
Then Carol might feel excluded, because it might sound like Alice is only referring to Barbara. Again, for French/Spanish/German speakers, imagine if you used "tu"/"tú"/"du" in this context.
In my dialect, we even have a possessive form: "your guys's," pronounced like "your guises" (/jɜr gaɪzəz/). There's no commonly-accepted written form that I'm aware of, so I'm winging it here.
For instance, in spoken English, this would be perfectly grammatical:
"Is the party at your guys's house?"
Whereas the following would imply that the house was only owned by one person:
"Is the party at your house?"
Side note: in my experience, though, it sounds weird if the phrase is used twice in the same sentence:
"Are you guys hosting the party at your guys's house?" * - sounds weird
In cases where the pronoun is repeated, it's okay to use "you" the second time. The plural meaning is still clear:
"Are you guys hosting the party at your house?" * - sounds better
In most contexts other than "you guys" and "your guys's", the word "guy" or "guys" is understood to refer only to men. So for instance, "She's like one of the guys" means that she gets along well with men, and "a nice guy" can only refer to a man.
There are some minor exceptions when "guys" is used to address a group of people. For instance, "Hey guys," "Good night, guys," "Guys!", etc. could be applied to a group of women as well as a group of men. But for the most part, the split is between "you guys"/"your guys's" and every other use of "guy"/"guys".
As noted in the Wikipedia article, many English dialects do not have "you guys"/"your guys's", and instead have their own second-person plural forms (accusative+nominative/possessive given):
- y'all/y'all's (US South)
- ye/yer (parts of Ireland)
- all y'all/all y'all's, you all/you all's, youse/youse's, etc.
In those dialects, "guys" always refers to men, unless they're watching a Hollywood movie, in which case their brains automatically switch to American mode. (My own brain has not yet accomplished the reverse feat when I watch Guy Ritchie movies.)
Languages change over time. "Guy" was originally a man's given name and not a generic term for men, let alone a semantically-bleached gender-neutral pronoun. My parents and grandparents do not use "you guys"/"your guys's" as consistently as I do, and I doubt my great-grandparents used them at all. In Shakespeare's time, the plural form was "you" and the singular form was "thou." No language's vocabulary is set in stone.
Also, none of this is a "100%" kind of rule – "you guys" is too much of a linguistic novelty to have fully conquered the language yet. For instance, there's a great scene in the TV show Freaks and Geeks, when a character uses "you guys" to refer to a group of men plus one formerly hermaphroditic woman – a woman who is trying to keep this fact a secret to everyone but her boyfriend. However, her boyfriend misunderstands, and angrily replies, "What do you mean, you guys?" The girlfriend is mortified.
The tragedy of the scene is that, if the boyfriend had said nothing, nobody would have noticed anything out of the ordinary. But once he points it out, he's inadvertently betrayed his girlfriend's secret. I think maybe the fact that the show takes place in the 80's might also contribute to the ambiguity of "guys" in this case.
Bottom line: if you don't want to cause confusion or offense to non-native English speakers or speakers of other English dialects, try to avoid using "you guys" online or in formal settings. Personally I like to use "y'all," because it's explicitly gender-neutral, and also I think it sounds cool.