"You are eating this sandwich."
Translation:Εσύ τρως αυτό το σάντουιτς.
What's the purpose of "αυτό" in this sentence? Would it work without it, as well?
The difference would be about the same as if you removed "this" from the English. The English would then need "a" but the Greek would not use the article.
and why not without the το? Like εσύ τρως αυτι σαντουιτσ? cause αυτι means this, right?
Αυτή is used only for feminine nouns. Sandwich (σάντουιτς) is considered neuter. In other words:
Αυτός (masc.), αυτή (fem.), αυτό (neut.).
And no, you definitely can't omit the article το in this case. It's a basic greek sentence structure when you're talking about one specific thing. You could only omit the article in really general cases, without the pronoun αυτός-ή-ό, like
-Εγώ πίνω γάλα - I drink milk (in general. You wouldn't say "πίνω αυτό το γάλα", unless you were referring to one specific bottle of milk.)
I hope I helped you a bit. ^.^
Because είσαι means you are in the sense of being. It's like saying "You are are eating/eat a sandwich" in English. It doesn't make sense. :p
Εσύ is the pronoun you should use for you, and τρως for eat/eating. Present Simple and Present Continuous are expressed by the same tense in Greek, Ενεστώτας.
I get that it doesn't really make sense to have an accent on a one-syllable word (i.e. there is only one possible way to pronounce the stress), but is writing τρώς incorrect or just redundant?
It's an error but not a hanging offense. But as a newcomer to the language you should try to avoid as many errors...even these small ones... as you can.
Well, if you're never going to see it written with an accent (at least not on any official text or a book), I'd say there's no point in adding that accent. ^.^