"Who are you?"

Translation: Ποιος είσαι;

[AnCatDubh]

Why not ποια?

[Daniel147471]

Is "Ποιος είναι;" who is it?

[JanetOlson3]

So, is this vocative case? I can't find it on your chart, and vocative is not included.

[jaye16]

The "vocative" is simply when we call someone to get his/her attention. E.g. Kosta come here for a minute. It's the simplest form of the name or word. See here for the cases:

https://www.greekgrammar.eu/pdffiles/cases.pdf

It's the last one on the page.

[MichaelTab411132]

Why είσαι as opposed to είσαστε? If asking "Who are you?"
isn't it rather likely to expect the formal over the informal?

[Michael834127]

The English sentence could be plural, referring to a group of people. Why is Ποιοι είσαστε; not a possible correct answer?