Συνήθως τρώω δημητριακά με γάλα για πρωινό.

Because Greek usually does not need an explicit subject pronoun when the verb ending already shows who is doing the action.

• τρώω = I eat / I am eating
• The ending -ω tells you it is 1st person singular.

So Συνήθως τρώω... already means Usually I eat...

You could add εγώ (I) for emphasis or contrast:

• Εγώ συνήθως τρώω δημητριακά. = I usually eat cereal.

But in a neutral sentence, leaving it out is more natural.

τρώω is the present tense, 1st person singular form of τρώω (to eat).

In this sentence, it means I eat in a habitual sense, not just right now. That is because of Συνήθως (usually).

So:

• τρώω can mean I eat
• or I am eating, depending on context

Here, with Συνήθως, it clearly means:

• I usually eat

Συνήθως means usually.

It does not have to go first, but putting it first is very common and natural. It sets the tone of the sentence right away.

You could also say:

• Τρώω συνήθως δημητριακά με γάλα για πρωινό.
• Για πρωινό συνήθως τρώω δημητριακά με γάλα.

All of these are possible, but the original sentence is very normal and straightforward.

In Greek, δημητριακά is very commonly used in the plural to mean cereal or breakfast cereal in a general sense.

Literally, it comes from the idea of cereals/grains, so the plural feels natural in Greek.

So:

• δημητριακά = cereal / cereals / breakfast cereal

Even if English often uses singular cereal, Greek commonly uses the plural form here.

Not always. δημητριακά can also refer more generally to cereals or grain products, depending on context.

But in a sentence like this:

• τρώω δημητριακά με γάλα για πρωινό

it very naturally means breakfast cereal.

So the context tells you the exact meaning.

Greek often leaves out the article with general, non-specific food items and in fixed expressions.

Here the speaker means food in a general way:

• δημητριακά = cereal in general
• γάλα = milk in general
• για πρωινό = for breakfast

If you were talking about something specific, an article could appear:

• Τα δημητριακά που αγόρασα είναι πολύ γλυκά. = The cereal I bought is very sweet.
• Το γάλα στο ψυγείο είναι χαλασμένο. = The milk in the fridge is spoiled.

So in the original sentence, no article sounds natural.

They are in the accusative, because of how they function in the sentence.

• δημητριακά = direct object of τρώω
• γάλα = object of the preposition με (with)
• πρωινό = object of the preposition για (for)

So grammatically:

• δημητριακά = accusative plural neuter
• γάλα = accusative singular neuter
• πρωινό = accusative singular neuter

A small note: for many neuter nouns in Greek, the nominative and accusative look the same, so the form does not visibly change.

με means with, so με γάλα means with milk.

It tells you what the cereal is eaten together with.

• δημητριακά με γάλα = cereal with milk

This is very direct and works just like English with milk.

Because πρωινό here means breakfast, while πρωί means morning.

So:

• για πρωινό = for breakfast
• το πρωί = in the morning

These are different ideas.

Compare:

• Συνήθως τρώω δημητριακά με γάλα για πρωινό.
  = I usually eat cereal with milk for breakfast.

• Το πρωί συνήθως τρώω δημητριακά με γάλα.
  = In the morning I usually eat cereal with milk.

Very similar meaning in practice, but not exactly the same structure.

Not exactly.

• πρωινό as a noun usually means breakfast
• πρωινός / πρωινή / πρωινό as an adjective means morning or morning-related

Examples:

• Το πρωινό είναι έτοιμο. = Breakfast is ready.
• η πρωινή εφημερίδα = the morning newspaper

So in για πρωινό, it is clearly the noun breakfast.

No, Greek word order is more flexible than English word order.

The original sentence is:

• Συνήθως τρώω δημητριακά με γάλα για πρωινό.

But Greek can move parts around for emphasis or style:

• Για πρωινό συνήθως τρώω δημητριακά με γάλα.
• Δημητριακά με γάλα τρώω συνήθως για πρωινό.

The original version is neutral and very natural for learners to use.

A rough English-friendly guide is:

see-NEE-thos TRO-o thee-mee-tria-KA me GA-la ya pro-ee-NO

A few notes:

• Συνήθως → stress on -νή-
• τρώω → stress on τρώ-
• δημητριακά → stress on final -κά
• πρωινό → stress on final -νό

The Greek stress marks show you which syllable is stressed, and they are important in writing.

That is just the standard spelling of the verb form.

• infinitive-style dictionary form: τρώω = to eat
• 1st person singular present: also τρώω = I eat

In pronunciation, those final vowels are not pronounced like a normal English single long vowel. The word is typically heard as something like TRO-o.

So even if the spelling looks unusual at first, it is a very common verb form and worth memorizing as a whole.

That would not mean the same thing.

• με γάλα = with milk
• και γάλα = and milk

So:

• δημητριακά με γάλα = cereal with milk together
• δημητριακά και γάλα = cereal and milk as two separate items

For the usual idea of cereal served with milk, με γάλα is the correct choice.