Learn Hardcore Greek: Το μεταπτυχιακό μου είναι δύσκολο αλλά ενδιαφέρον. - My master’s program is difficult but interesting.

Το – the (neuter singular definite article)
μεταπτυχιακό – postgraduate / master’s (program/degree) (neuter noun here)
μου – my (unstressed possessive pronoun, “of me”)
είναι – is
δύσκολο – difficult / hard (neuter singular adjective)
αλλά – but
ενδιαφέρον – interesting (neuter singular adjective)

So literally: “The postgraduate (degree) of-me is difficult but interesting.”
Natural English: “My master’s (program) is difficult but interesting.”

Why is the possessive μου after the noun (μεταπτυχιακό μου) instead of before it, like in English “my master’s”?

In Greek, unstressed (clitic) possessive pronouns like μου, σου, του, της, μας, σας, τους normally come after the noun:

το βιβλίο μου – my book
η μητέρα σου – your mother
το μεταπτυχιακό μου – my master’s (program)

Putting μου before the noun (μου μεταπτυχιακό) is ungrammatical in standard Greek. The “my” idea is expressed by this post‑positioned clitic, not a separate word before the noun as in English.

Why do we need Το (“the”) if the noun already has μου (“my”)? In English we don’t say “the my master’s”.

Greek normally uses the definite article with possessive pronouns:

το βιβλίο μου – my book
η φίλη μου – my (female) friend
το μεταπτυχιακό μου – my master’s

Leaving out the article (μεταπτυχιακό μου είναι δύσκολο…) is possible only in certain more marked or poetic styles; in everyday standard speech it sounds wrong or at least very odd.

So in Greek the “default” pattern is:
article + noun + possessive = English my/your/his/her + noun.

What exactly is μεταπτυχιακό? Is it just “Master’s”, or any postgraduate degree?

μεταπτυχιακό comes from:

μετά – “after”
πτυχίο – “degree” (usually bachelor’s)

So μεταπτυχιακό means “postgraduate (thing)”. In practice:

κάνω μεταπτυχιακό – I’m doing a master’s degree
το μεταπτυχιακό μου – my master’s program / postgraduate degree

In everyday modern Greek, το μεταπτυχιακό almost always refers to a Master’s level program or degree, not a PhD. A PhD is usually διδακτορικό (δίπλωμα).

Why are δύσκολο and ενδιαφέρον in the neuter form? Do they agree with something?

Yes. Adjectives in Greek agree with the gender, number, and case of the noun they describe.

μεταπτυχιακό is a neuter singular noun.
So the adjectives describing it must also be neuter singular:
- δύσκολος (m.), δύσκολη (f.), δύσκολο (n.)
  → here we use δύσκολο (neuter)
- ενδιαφέρων (m.), ενδιαφέρουσα (f.), ενδιαφέρον (n.)
  → here we use ενδιαφέρον (neuter)

So:
Το μεταπτυχιακό (neuter) μου είναι δύσκολο (neuter) αλλά ενδιαφέρον (neuter).

They both agree with το μεταπτυχιακό.

Why isn’t είναι repeated before ενδιαφέρον? Could I say είναι δύσκολο αλλά είναι ενδιαφέρον?

Greek works like English here:

English: My master’s is hard but interesting (not usually is hard but is interesting).
Greek: Το μεταπτυχιακό μου είναι δύσκολο αλλά ενδιαφέρον.

One είναι links the subject (το μεταπτυχιακό μου) with both adjectives (δύσκολο and ενδιαφέρον) joined by αλλά.

You can say:

Το μεταπτυχιακό μου είναι δύσκολο αλλά είναι ενδιαφέρον.

It’s grammatically correct, but it sounds more heavy or emphatic, like you’re stressing the contrast strongly:
“It’s hard, but (still, it really) is interesting.”

In neutral speech, the version with a single είναι is more natural.

What’s the exact role of αλλά here? How is it different from και or όμως?

αλλά is the basic conjunction meaning “but”, introducing a contrast:

είναι δύσκολο αλλά ενδιαφέρον – it is difficult but interesting

Compared:

και – “and”, simply adds information with no contrast:
- είναι δύσκολο και ενδιαφέρον – it is difficult and interesting
  (both are true, presented as compatible, not opposed)
όμως – “however / though / but”; it’s an adverb, not a conjunction. You’d usually put it in a separate clause or in a different position:
- Το μεταπτυχιακό μου είναι δύσκολο. Όμως είναι ενδιαφέρον.
  – My master’s is difficult. However, it is interesting.

In your sentence, αλλά is the natural choice to show a direct contrast in the same clause.

How do you pronounce μεταπτυχιακό? The πτυχ cluster looks tricky.

μεταπτυχιακό is stressed on the last syllable:
με‑τα‑πτη‑χια‑ΚΌ → /me-ta-pti-xi-a-ˈko/

Tips:

πτ = /pt/ (like “pt” in apt but in the middle of the word)
χ before ι/ε is like the German ch in ich, or the Spanish j in jefe, but softer: /ç/
ια is two sounds: /i.a/ → “ee‑a”

Syllables: με‑τα‑πτι‑χια‑κό
Try slowly: με‑τα – πτι – χια – κό, then speed up.

Why is it ενδιαφέρον here and not ενδιαφέρων (like in some dictionaries)?

Greek adjectives are usually listed in dictionaries with the masculine form, nominative singular:

ενδιαφέρων (m.)
ενδιαφέρουσα (f.)
ενδιαφέρον (n.)

In your sentence, the subject το μεταπτυχιακό is neuter, so you must use the neuter form:

ενδιαφέρον – interesting (neuter singular)

So:

ενδιαφέρων καθηγητής – an interesting (male) professor (masc.)
ενδιαφέρουσα διάλεξη – an interesting lecture (fem.)
ενδιαφέρον μεταπτυχιακό – an interesting master’s program (neut.)

How would I say this in the plural, e.g. “My master’s degrees are difficult but interesting”?

Make everything agree in neuter plural:

το μεταπτυχιακό → τα μεταπτυχιακά (the master’s degrees/programs)
είναι stays the same (it’s used for both singular and plural)
δύσκολο → δύσκολα (neuter plural)
ενδιαφέρον → ενδιαφέροντα (neuter plural)

Full sentence:

Τα μεταπτυχιακά μου είναι δύσκολα αλλά ενδιαφέροντα.
– My master’s degrees/programs are difficult but interesting.

Can I change the word order to Το δύσκολο αλλά ενδιαφέρον μεταπτυχιακό μου? Is that still correct?

Yes, that’s grammatical, but the nuance changes.

Το μεταπτυχιακό μου είναι δύσκολο αλλά ενδιαφέρον.
- Neutral statement. You’re just describing it: My master’s is difficult but interesting.
Το δύσκολο αλλά ενδιαφέρον μεταπτυχιακό μου…
- This sounds like you are introducing or specifying “my difficult but interesting master’s program” as a noun phrase, usually followed by something else:
  - Το δύσκολο αλλά ενδιαφέρον μεταπτυχιακό μου ξεκινά τον Οκτώβριο.
    – My difficult but interesting master’s program starts in October.

So your original sentence is a full statement with a verb.
The reordered version is a noun phrase with adjectives that typically needs more context or a following verb.