Στο σπίτι ζεσταίνω το φαγητό στα μικροκύματα, όταν δεν έχω χρόνο να μαγειρέψω.

Στο is the contracted form of σε + το.

• σε = in, at, to
• το = the (neuter singular)

So στο σπίτι literally means in/at the house, but very naturally it means at home.

Greek very often contracts σε with the definite article:

• σε + το → στο
• σε + τα → στα
• σε + τη(ν) → στη(ν)
• σε + τον → στον

So σε το σπίτι would sound unnatural in normal Greek.

Greek often uses σπίτι (house/home) in expressions where English uses home without an article.

So:

• στο σπίτι = at home / in the house

This is a very common Greek expression. Even though it literally contains the, the natural English translation is often just at home.

Ζεσταίνω is:

• 1st person singular
• present tense
• active voice

So it means I heat / I warm up.

In this sentence, the present tense expresses a habit or something you do regularly:

• Στο σπίτι ζεσταίνω το φαγητό...
• At home, I heat up the food...

It is not necessarily happening right now; it can mean this is what I usually do.

Greek uses the definite article much more often than English does.

So το φαγητό literally means the food, but in context it can simply mean the food/meal I’m dealing with. Greek often prefers the article when talking about a specific, understood thing.

Compare:

• ζεσταίνω το φαγητό = I heat up the food / my food / the meal
• ζεσταίνω φαγητό = I heat food

The version with the article sounds more natural here because it refers to a particular meal.

Yes, μικροκύματα is grammatically plural, and that often confuses learners.

In everyday Greek, στα μικροκύματα means in the microwave or using the microwave.

This comes from the fuller expression related to microwaves as a technology, and in modern speech Greeks commonly use:

• βάζω κάτι στα μικροκύματα
• ζεσταίνω κάτι στα μικροκύματα

So although English uses singular microwave, Greek commonly uses the plural form τα μικροκύματα in this expression.

A more explicit version would be something like στον φούρνο μικροκυμάτων = in the microwave oven, but everyday Greek usually shortens it to στα μικροκύματα.

Όταν can mean both when and whenever, depending on context.

In this sentence, because the main verb is in the present and the idea is habitual, όταν is best understood as:

• when
• or more naturally, whenever

So:

• όταν δεν έχω χρόνο να μαγειρέψω
• when / whenever I don’t have time to cook

It introduces a time clause.

In Greek, δεν normally comes directly before the finite verb in ordinary statements.

So:

• δεν έχω = I do not have

That is the standard position. Greek negation is much less flexible than English in this respect.

Examples:

• δεν ξέρω = I don’t know
• δεν μπορώ = I can’t
• δεν έχω χρόνο = I don’t have time

Modern Greek does not use the infinitive the way English does. Instead, it usually uses να + a finite verb form.

So where English says:

• to cook

Greek says:

• να μαγειρέψω

This construction is often called the subjunctive or να-clause.

After expressions like έχω χρόνο (I have time), Greek uses this structure:

• έχω χρόνο να... = I have time to...
• δεν έχω χρόνο να... = I don’t have time to...

So δεν έχω χρόνο να μαγειρέψω means I don’t have time to cook.

This is an aspect question.

• να μαγειρέψω = aorist/perfective aspect
• να μαγειρεύω = present/imperfective aspect

Here, να μαγειρέψω treats cooking as a whole, complete action: to cook a meal.

That is the natural choice after δεν έχω χρόνο because the meaning is:

• I don’t have time to cook (a meal / something proper).

If you said να μαγειρεύω, it would sound more like:

• to be cooking
• to cook regularly
• to spend time cooking

That is possible in some contexts, but less natural in this sentence.

Greek word order is more flexible than English word order, but different orders can change the emphasis.

The sentence begins with Στο σπίτι to set the scene:

• Στο σπίτι ζεσταίνω το φαγητό...
• At home, I heat up the food...

That sounds natural and emphasizes the location first.

Other orders are possible, for example:

• Ζεσταίνω το φαγητό στα μικροκύματα στο σπίτι...

But that version sounds less natural for this context unless you specifically want to emphasize something different.

So the original word order is normal and idiomatic.

The comma separates the main clause from the following subordinate time clause:

• Στο σπίτι ζεσταίνω το φαγητό στα μικροκύματα,
• όταν δεν έχω χρόνο να μαγειρέψω.

This is very common in Greek punctuation, especially when the subordinate clause comes after the main clause.

You may also see the reverse order:

• Όταν δεν έχω χρόνο να μαγειρέψω, στο σπίτι ζεσταίνω το φαγητό στα μικροκύματα.

In that case, the comma comes after the first clause.

It is pronounced roughly:

• mi-kro-KY-ma-ta

The stress is on κύ.

A rough English approximation is:

• mee-kroh-KYOO-mah-tah

The letter combination κυ here sounds like ky.

Yes, ζεσταίνω is the most natural everyday verb here.

• ζεσταίνω = heat up, warm up
• θερμαίνω = heat

Θερμαίνω is more formal, technical, or scientific. In daily speech, if you are talking about reheating food, ζεσταίνω is the normal choice.

So:

• ζεσταίνω το φαγητό = I heat up the food / I warm up the food

That sounds exactly right for reheating something in the microwave.