Learn Hardcore Greek: Το χαλί είναι μπλε, αλλά η αδερφή μου θέλει το δικό της χαλί να είναι κόκκινο. - The carpet is blue, but my sister wants her own carpet to be red.

Το χαλί είναι μπλε. = The carpet is blue. (you’re talking about a specific carpet)
Η αδερφή μου is the normal way to say my sister; αδερφή μου without η is possible but feels less complete or more “headline-style” / poetic.

So in normal everyday speech, you almost always keep the article with nouns like this.

Why is it η αδερφή μου and not μου αδερφή (like “my sister”)?

In Greek, the weak possessive pronouns (μου, σου, του, της, μας, σας, τους) usually come after the noun, not before it.

So:

η αδερφή μου = my sister
το χαλί της = her carpet

Putting μου or της before the noun (μου αδερφή) is not normal modern Greek. If you want to put something before the noun for emphasis, you use δικός / δικιά / δικό, e.g. η δικιά μου αδερφή (my own sister).

What is the difference between αδερφή and αδελφή?

They are the same word: sister.

αδερφή is the more modern, phonetic spelling. It’s what you will hear in everyday speech.
αδελφή is the older, more “traditional” spelling and is still common in more formal or religious contexts, or in writing.

Pronunciation is practically the same in modern Greek; you can think of αδερφή as the everyday form.

Why do we say το δικό της χαλί instead of just το χαλί της?

Both are grammatically correct, but they give slightly different nuances:

το χαλί της = her carpet (neutral statement of possession)
το δικό της χαλί = her own carpet (emphasis that it’s hers, not someone else’s)

So the full sentence:

…αλλά η αδερφή μου θέλει το δικό της χαλί να είναι κόκκινο.

implies a contrast: my carpet is blue, but my sister wants *her own carpet to be red (not mine).*

Why is it δικό της and not δική της or δικός της?

The word δικός / δικιά (ή δική) / δικό must agree in gender, number, and case with the thing that is owned, not with the owner.

Here, the thing is το χαλί (neuter singular):

neuter singular → δικό
feminine singular would be → δικιά or δική
masculine singular would be → δικός

So you get:

το δικό της χαλί
- το (neuter singular article)
- δικό (neuter singular, agreeing with χαλί)
- της (her)

If the noun were feminine, e.g. η καρέκλα (the chair), you’d say η δικιά της καρέκλα.

Do we always need both το and της when we use δικό της?

The structure in full is:

[article] + [δικός/δικιά/δικό] + [possessive pronoun] + [noun]

So here:

το δικό της χαλί

You can:

drop the noun, if it’s clear:
- Το δικό της είναι κόκκινο. = Hers is red. (meaning: her carpet)
but you normally keep the article and the possessive, because they’re part of the structure of this emphatic “own” form.

Saying just δικό της χαλί (without το) is possible but sounds more informal or incomplete; the article is very common and natural.

Why do we have να είναι after θέλει? Why not just θέλει είναι κόκκινο?

Modern Greek does not use an infinitive like English to be. Instead, it uses να + subjunctive.

So where English says:

She wants her carpet *to be red.*

Greek says:

θέλει το δικό της χαλί να είναι κόκκινο.

Here:

να is a particle that introduces a subordinate clause (similar to English to or that in this kind of sentence).
είναι is the verb είμαι (to be).

You generally cannot say θέλει είναι κόκκινο; you need να there: θέλει να είναι κόκκινο.

Is είναι after να a special subjunctive form? It looks the same as the normal είναι.

For the verb είμαι (to be), the present subjunctive form is identical to the present indicative:

(εγώ) είμαι
(εσύ) είσαι
(αυτός/αυτή/αυτό) είναι
…

Subjunctive is shown by the particle να, not by a different verb ending here.

So:

Το χαλί είναι μπλε. → είναι = indicative (is)
…να είναι κόκκινο. → είναι = subjunctive (to be)

Same spelling and pronunciation, different function because of να.

In θέλει το δικό της χαλί να είναι κόκκινο, what is the subject of είναι?

The subject of είναι (in να είναι κόκκινο) is το δικό της χαλί.

You can think of the structure as:

Η αδερφή μου (subject of θέλει)
θέλει (main verb)
[το δικό της χαλί] (the thing she is talking about)
να είναι κόκκινο (what she wants that thing to be)

So the subject is understood from context; it doesn’t get repeated in the second clause. Greek does this very often.

Why is μπλε the same form here, but κόκκινο ends in -ο? Don’t adjectives usually change?

Most Greek adjectives change their ending to agree with the noun:

masculine: κόκκινος
feminine: κόκκινη
neuter: κόκκινο

Here χαλί is neuter, so you get κόκκινο.

But some adjectives (especially many color words borrowed from French) are indeclinable, meaning they keep the same form for all genders and cases. μπλε is one of those:

το χαλί είναι μπλε
η καρέκλα είναι μπλε
ο τοίχος είναι μπλε

All use μπλε, unchanged.

Why is it κόκκινο and not κόκκινος or κόκκινη?

Because κόκκινο must agree with the (understood) noun, which is το χαλί (neuter singular).

χαλί → neuter singular
neuter singular adjective form → κόκκινο

If the noun were masculine or feminine, the adjective would change:

ο καναπές είναι κόκκινος (masc.)
η κουρτίνα είναι κόκκινη (fem.)
το χαλί είναι κόκκινο (neut.)

In your sentence, even though χαλί isn’t repeated after κόκκινο, its gender still controls the adjective form.

Can the word order change? For example, can I say Η αδερφή μου θέλει το χαλί της να είναι κόκκινο or Η αδερφή μου το θέλει κόκκινο?

Yes, several variations are possible and natural, with small differences in emphasis:

Η αδερφή μου θέλει το χαλί της να είναι κόκκινο.
- Same meaning, but without the extra emphasis on “her own carpet”. Just her carpet.
Η αδερφή μου το θέλει κόκκινο.
- Literally: My sister wants it red.
- το here stands for το χαλί. This is fine if it’s already clear what “it” is.
You can also slightly move things around:
- Η αδερφή μου θέλει να είναι κόκκινο το δικό της χαλί.
  (a bit more marked/emphatic, focusing on κόκκινο.)

All of these are grammatical; Greek word order is relatively flexible, but the original version is very natural and clear.