Learn Hardcore Greek: Το παχύ γιαούρτι με μέλι είναι πολύ νόστιμο το πρωί. - Thick yogurt with honey is very tasty in the morning.

Το παχύ γιαούρτι με μέλι = “(the) thick yogurt with honey” in a general sense: thick yogurt-with-honey as a type.
In English, we usually drop the in this kind of generic statement, but in Greek you normally keep the article.

So το here:

Marks that παχύ γιαούρτι με μέλι is the subject.
Shows we’re talking about yogurt in general, not about some specific portion that is in front of us.

Why are το, παχύ, γιαούρτι all neuter?

Because the noun γιαούρτι (yogurt) is grammatically neuter in Greek:

το γιαούρτι – neuter singular (nominative)
Any adjective that goes with it must also be neuter singular.

So we get:

το (neuter article)
παχύ (neuter adjective: “thick/fatty”)
γιαούρτι (neuter noun)

All three agree in:

gender: neuter
number: singular
case: nominative (because they form the subject of the sentence)

What exactly does παχύ mean here? Is it “thick”, “fatty”, or “full-fat”?

παχύ literally means “thick” or “fatty”, and with γιαούρτι it usually implies “full‑fat, creamy, thick yogurt”.

Common terms:

παχύ γιαούρτι – thick / full-fat yogurt (creamy, higher fat)
στραγγιστό γιαούρτι – strained yogurt (the typical Greek yogurt style)
πυκνό – “dense, thick” in a more general sense (not only for yogurt)

In everyday speech, παχύ γιαούρτι is very natural for rich, creamy yogurt like Greek yogurt.

Why is νόστιμο also neuter? Shouldn’t it be masculine like νόστιμος?

νόστιμο agrees with the subject το παχύ γιαούρτι με μέλι, which is neuter singular.

Adjective pattern:

Masculine: νόστιμος
Feminine: νόστιμη
Neuter: νόστιμο

Because the subject is το γιαούρτι (neuter), the predicative adjective must match:

Το παχύ γιαούρτι με μέλι είναι πολύ νόστιμο.
(Thick yogurt with honey is very tasty.)

You would only use νόστιμος if the subject were a masculine noun, e.g.:

Ο καφές είναι νόστιμος. – The coffee is tasty.

What does πολύ do here? Is it “very”, “much”, or “a lot”?

In this sentence πολύ functions as an adverb meaning “very”:

είναι πολύ νόστιμο = “is very tasty”

The word πολύ can be:

An adverb: Τρέχει πολύ. – He runs a lot / very fast.
An adjective: πολύς χρόνος – much time.

Here it clearly modifies the adjective νόστιμο, so the meaning is “very tasty”, and the English translation “delicious” is also a good natural equivalent.

Why is it με μέλι and not με το μέλι?

Both are possible, but they don’t mean exactly the same:

με μέλι – with (some) honey, honey in general, not specified
με το μέλι – with the honey (some specific honey that both speaker and listener know about)

In your sentence, we’re talking about the combination “yogurt with honey” as a general idea, so Greek normally omits the article:

Το παχύ γιαούρτι με μέλι είναι πολύ νόστιμο το πρωί.
Thick yogurt with honey (as a type) is very tasty in the morning.

Why does το πρωί mean “in the morning” when there is no word for “in”?

Greek often uses a bare accusative of time with the definite article to mean “in/at [time]”.

Common patterns:

το πρωί – in the morning
το βράδυ – in the evening / at night
το μεσημέρι – at noon / midday

So:

είναι πολύ νόστιμο το πρωί
literally: “it is very tasty the morning”
meaning: “it is very tasty in the morning.”

You could also say το πρωί είναι πολύ νόστιμο, moving το πρωί to the front, but the meaning is the same.

What cases are the nouns γιαούρτι, μέλι, and πρωί in?

In this sentence:

γιαούρτι – nominative singular neuter
- It is the core of the subject: Το παχύ γιαούρτι με μέλι.
μέλι – accusative singular neuter
- After the preposition με: με μέλι (“with honey”).
- For neuter nouns, nominative and accusative look the same, but here the function is object of με.
πρωί – accusative singular neuter
- το πρωί is accusative of time (“in the morning”).

So:

Subject (nominative): Το παχύ γιαούρτι με μέλι
Prepositional object (accusative): με μέλι
Time expression (accusative of time): το πρωί

Is the whole phrase Το παχύ γιαούρτι με μέλι the subject of the sentence?

Yes.

Subject:

Το παχύ γιαούρτι με μέλι – Thick yogurt with honey

Predicate:

είναι πολύ νόστιμο το πρωί – is very tasty in the morning

So the structure is:

[Subject] Το παχύ γιαούρτι με μέλι
[Verb] είναι
[Predicate adjective] πολύ νόστιμο
[Time] το πρωί

Can I change the word order? For example, can I say Το παχύ γιαούρτι είναι πολύ νόστιμο με μέλι το πρωί?

You can change the word order, but it may change the emphasis or even sound odd.

Original:

Το παχύ γιαούρτι με μέλι είναι πολύ νόστιμο το πρωί.
The yogurt-with-honey is what’s tasty in the morning.

Your version:

Το παχύ γιαούρτι είναι πολύ νόστιμο με μέλι το πρωί.
This sounds more like: “Thick yogurt is very tasty with honey in the morning” – i.e. yogurt is tasty in the morning when you eat it with honey, instead of describing “yogurt-with-honey” as one fixed combination.

Both are understandable, but the original is smoother and more natural as a fixed phrase about that specific combination.

How would I say “Thick yogurts with honey are very tasty in the morning” in Greek?

You would put the noun and adjectives in the plural, neuter:

Τα παχιά γιαούρτια με μέλι είναι πολύ νόστιμα το πρωί.

Changes:

Το → Τα (neuter plural article)
παχύ → παχιά (neuter plural form of the adjective)
γιαούρτι → γιαούρτια (plural of “yogurt”)
νόστιμο → νόστιμα (neuter plural adjective to agree with γιαούρτια)