"Ποιος είναι αυτός;"

Translation: Who is he?

[cPR512]

Ποιός είναι αυτός; Who is this? Or he?

[GreekEman2018]

How would you say "which is this?" ?

[D_..]

Ποιο είναι αυτό; since it refers to a thing.
You can still refer to masculine/feminine things with ποιος/ποια but you need the right context: Ποια είναι η σαλάτα μου;

[JamesTWils]

How would one say "who is this?"

[c14p]

If you mean 'this' as in someone being in the same place as you, or in a photo you are pointing at, for instance, then you'd use the same sentence to ask a third person about him/her. :)

But in case you are thinking about ''Who's this?'' in the sense of 'Who is this/it (that I am talking to)'' while you are addressing someone directly, then you'd have to use the second person (singular or plural, depends on the level of formality)

Hope this helped?

[philipduerdoth]

But not that horrible English question: And you are? :-)

[TobyBartels]

Why yes, I am, thanks for noticing.

[philipduerdoth]

But do you not agree that 'And you are?' sounds quite rude and even dismissive?

[JamesTWils]

I imagine I am rather tone deaf to this, as people seem to strive to take offense to things I cannot see as offensive, but is that phrase ruder or more dismissive than "And who are you?"

[philipduerdoth]

Probably not, James. It depends on the tone it's delivered with. On paper you don't get the difference between a friendly question, and the seemingly unfriendly version. Perhaps best to reword it.

[JamesTWils]

It helped a great deal. I was counted off for translating it that way and reported it, but then I wasn't confident that I should have.