Y'all is the American informal second-person plural pronoun
Spanish: "ustedes" (formal) and "vosotros" (informal in Spain) or "vos" in some regions
French: "vous" is the standard, but informally there's "vous autres" in Quebec French
Portuguese: "vocês" formally, but "cês" informally in Brazilian Portuguese
German: While "ihr" is standard, some dialects use "ihr alle" or regional variants
Italian: "voi" is standard, but some southern dialects use "vujatri" or similar variants
Greek: "εσείς" (eseis) formally, but informally "εσείς όλοι" (eseis oli)
Russian: "вы" (vy) is standard, but "вы все" (vy vse) is used for emphasis
Arabic: "أنتم" (antum) is standard, with "إنتو" (intu) in dialects
I am most fascinated by Y'alls', a double possessive or possessive plural contraction which is common in Southern American English and AAVE (African American Vernacular English) which would otherwise be constructed more awkwardly in common American English as "all of your" or "your all's."
Vous is also the polite singular second person pronoun in French so they are part way to losing the singular.
I did not know the abbreviation "AAVE" but its always struck me as odd how much a shared language has split along racial lines. I wonder whether there are similar things elsewhere. Obviously where people speak English as a second language and speak different first language they might speak it a bit differently, as might (recent) immigrant communities, but those are both very different.
(Sidenote: when we were teenagers my sister and I referred to one pastor as "the polytheist", because he always said "in Jesus's name", which we chose to interpret as "in Jesuses' name". God, I'm a nerd.)
Spanish: "ustedes" (formal) and "vosotros" (informal in Spain) or "vos" in some regions
French: "vous" is the standard, but informally there's "vous autres" in Quebec French
Portuguese: "vocês" formally, but "cês" informally in Brazilian Portuguese
German: While "ihr" is standard, some dialects use "ihr alle" or regional variants
Italian: "voi" is standard, but some southern dialects use "vujatri" or similar variants
Greek: "εσείς" (eseis) formally, but informally "εσείς όλοι" (eseis oli)
Russian: "вы" (vy) is standard, but "вы все" (vy vse) is used for emphasis
Arabic: "أنتم" (antum) is standard, with "إنتو" (intu) in dialects
I am most fascinated by Y'alls', a double possessive or possessive plural contraction which is common in Southern American English and AAVE (African American Vernacular English) which would otherwise be constructed more awkwardly in common American English as "all of your" or "your all's."