Learn Hardcore Greek: Δεν θυμάται την ίδια ιδέα, δυστυχώς. - He doesn't remember the same idea, unfortunately.

It is 3rd person singular, present tense, of the mediopassive verb θυμάμαι (to remember). The ending -ται marks 3rd singular in the mediopassive. Although it’s mediopassive in form, its meaning here is active: “he/she/it remembers.”

Where is the subject pronoun? How do I know who “doesn’t remember”?

Greek is a pro‑drop language: subject pronouns are usually omitted. Δεν θυμάται can mean “he doesn’t remember,” “she doesn’t remember,” or “it doesn’t remember,” depending on context. You add a pronoun only for emphasis or clarity: Αυτός/Αυτή δεν θυμάται…

Why δεν and not μην?

Use δεν to negate indicative statements and questions: Δεν θυμάται…
Use μην with the subjunctive/with να, with negative commands, and in certain set environments:

Μην θυμηθείς! (Don’t remember! — grammatically fine, though uncommon as an idea)
Μην το ξεχάσεις! (Don’t forget it!)
Να μην το ξεχάσει. (So that he/she doesn’t forget it.)

Can I write δε θυμάται instead of δεν θυμάται?

Yes, in informal writing/speech the final -ν of δεν is often dropped before many consonants, so δε θυμάται is common. In careful/standard writing, δεν is always correct.

Why is it την ίδια ιδέα and not τη ίδια ιδέα? When do we keep the final -ν?

With the feminine article την, the final -ν is kept before:

vowels and
the consonants κ, π, τ, ξ, ψ, μπ, ντ, γκ, τσ, τζ.

Since ίδια starts with a vowel (ι), we keep the -ν: την ίδια ιδέα.

Why ίδια and not ίδιο?

Agreement. Ιδέα is feminine singular, so the adjective “same” must match: ίδιος (masc.), ίδια (fem.), ίδιο (neut.). Here: την ίδια ιδέα.

Do I need the article? Can I say Δεν θυμάται ίδια ιδέα?

You need the article. In Greek, attributive adjectives normally appear inside an article–noun group. Δεν θυμάται την ίδια ιδέα is natural; Δεν θυμάται ίδια ιδέα sounds ungrammatical/unnatural.

What’s the difference between η/την ίδια ιδέα and το ίδιο?

την ίδια ιδέα = “the same idea” (adjective + noun).
το ίδιο = “the same (thing)” (neuter pronoun/adverbial use).
So you can also say: Δεν θυμάται το ίδιο. (“He/She doesn’t remember the same thing.”)

How do I pronounce the tricky parts?

Δεν = [ðen] (δ like th in “this”).
θυμάται = [θiˈma.te] (θ like th in “think”; αι = [e], not [ai]).
ίδια = [ˈiðʝa] (δ = [ð]; γ before ι ≈ [ʝ], a “y”-like sound).
ιδέα = [iˈðe.a] (two syllables at the end: de‑a).
δυστυχώς = [ðustiˈxos] (χ = rough “kh,” as in German “Bach”).

Where can δυστυχώς go, and do I need the comma?

It’s a sentence adverb meaning “unfortunately,” often set off by a comma:

Δυστυχώς, δεν θυμάται την ίδια ιδέα.
Δεν θυμάται την ίδια ιδέα, δυστυχώς.
Without a comma it’s less parenthetical, but the comma is common and recommended.

Does Δεν θυμάται mean “can’t remember” as well as “doesn’t remember”?

Often yes in everyday English translation. If you want to emphasize inability, use: Δεν μπορεί να θυμηθεί (“cannot remember”). The simple Δεν θυμάται is the usual, neutral way to say it.

How do I say “the same idea as me/her/them”?

Use με for “as”:

την ίδια ιδέα με εμένα/με μένα (as me)
την ίδια ιδέα με εκείνη(ν) (as her)
την ίδια ιδέα με αυτούς/με αυτές (as them)

How do I replace the object with a pronoun?

Since ιδέα is feminine, use τη(ν): Δεν τη θυμάται, δυστυχώς. (“He/She doesn’t remember it.”)
If you front the object for emphasis, Greek often doubles with a clitic: Την ίδια ιδέα δεν τη θυμάται.

How do I put this in the past?

Aorist (single completed event): Δεν θυμήθηκε την ίδια ιδέα.
Imperfect (ongoing/state in the past): Δεν θυμόταν την ίδια ιδέα.

How do I turn it into a yes/no question: “Doesn’t he/she remember the same idea?”

Keep the word order and use a question mark (in Greek typography, a semicolon):
Δεν θυμάται την ίδια ιδέα;
Intonation does the rest.

Are θυμάται and θυμάτε the same in pronunciation?

Yes, both are pronounced [θiˈma.te]. θυμάται = 3rd person singular; θυμάτε = 2nd person plural (you all remember). Context and spelling distinguish them.

Is there a more emphatic way to say “the very same idea”?

Yes: την ίδια την ιδέα or, in subject position, η ίδια η ιδέα. The doubled article + adjective adds emphasis: “the very idea.”

Is there any spelling pitfall with ίδια?

Don’t confuse ίδια (“same”) with ιδία (learned/archaic form related to “private,” as in κατ’ ιδίαν = “in private”). For “same,” use ίδια.