"What had you eaten?"

Translation: Τι είχες φάει;

[NikosNY]

Τι είχατε φάει is right as well - it could be either singular or plural

[Theo_Matrakas]

Right!!! Corrected ;)

[Zocbll]

Why is τρώει wrong?

[G.Georgopoulos]

"φάει" is the form used with the auxiliary verb "to have". "Τρώει" means "he/she/it eats/is eating".

[uoLL8]

Forgive me if I make you repeat things in common. I think saying "what did you eat" is the same thing. But maybe "what had you eat" is the same also. Both refer to the past. What I understand wrong;

Please help!

[jaye16]

There is a difference. "What did you eat." is simple and that's all.

But "What had you eaten." refers to something that happened before something else and it's important to show that it happened before. Είναι σημαντικό να δείξουμε ότι συνέβη πριν.

For example: "My stomach hurt last night." "What had you eaten." In other words, "before your stomach hurt".

Το στομάχι μου πόνεσε χθες το βράδυ." "Τι είχες φάει." Με άλλα λόγια, "Τι είχες φάει πριν πονέσεις το στομάχι σου"

Past perfect us only used when it's important to show something that happened before something else.

"The plane had left when I got to the airport." "Το αεροπλάνο είχε φύγει όταν έφτασα στο αεροδρόμιο." Δηλαδή είχα χάσει το αεροπλάνο.

Hope that helps.

[uoLL8]

You know very well that you are helping my dear teacher.

Thank you.

[dieter667754]

Would it also be possible to say "Ποιο είχες φάει"?

[D_..]

No, there is nothing to support Ποιο here so even the Greek is literally 'what'. Remember that ποιος/ποια/ποιο basically mean who/which out of a set of known options. These options support the use of the pronoun. E.g. - Υπήρχαν πολλά φαγητά στον μπουφέ. - Ποιο (φαγητό) δοκίμασες;
Here however, the answer could be Nothing or even Dirt! If anything goes, you can use 'Τι'. There are exceptions of course, as always: e.g. Τι θερμοκρασία έχει έξω; Τί ώρα είναι; You could argue that there is a limited range of temperatures or ways to define local time but it's still in the realm of infinite possible answers.

Consider also the difference in the following (strikethrough indicates words that can be omitted without losing any meaning):
- Αγόρασα ένα καινούργιο τραπέζι.
- Τι τραπέζι αγόρασες; (i.e. what type of table, end table, kitchen etc.)
- Τραπέζι Κουζίνας. Πήγα στο μαγαζί χ.
- Α, έχει πολύ ωραία τραπέζια εκεί, τα έχω δει. Ποιο πήρες; (i.e. which of the known set of table models we're talking about)
- Αυτό που διαφημίζει στη βιτρίνα. (διαφημίζει is in active voice because το μαγαζί is implied)

[dieter667754]

Thank you for your effort! Your info helped me an important step forward :-)

I'll keep in mind that Ποιος basically goes with a known set of options you can have in mind, even if they are not mentioned directly.....( beside the exceptions you explained).