Το στήθος του είναι ζεστό.

In Greek, body parts and many other possessed nouns are very often expressed as:

definite article + noun + weak possessive pronoun

So:

Το στήθος του = literally something like the chest of him, but naturally it means his chest.

This is completely normal Greek. You do not usually translate the article separately into English in this kind of phrase.

A very common pattern is:

• το χέρι μου = my hand
• τα μάτια της = her eyes
• το κεφάλι του = his head

So in this sentence, το is exactly what you should expect.

Here του is a weak possessive pronoun, and it means:

• his
• sometimes also its, depending on context

In this sentence, του goes after the noun:

• το στήθος του = his chest

Grammatically, this του comes from the genitive form of the pronoun, so you can think of it as meaning of him.

Compare:

• το βιβλίο του = his book
• η μητέρα του = his mother
• το σπίτι του = his house

So even though English puts his before the noun, Greek often puts του after it.

Because στήθος is simply a neuter noun in Greek. Noun gender in Greek is a grammatical category, and it does not always match natural gender.

The basic form is:

• το στήθος = the chest

Since it is neuter, words that go with it also appear in neuter forms, such as:

• το for the article
• ζεστό for the adjective

So the sentence is neuter all the way through because the noun στήθος is neuter.

Greek adjectives must agree with the noun they describe in gender, number, and case.

Here the noun is:

• το στήθος
• neuter
• singular

So the adjective must also be neuter singular:

• masculine: ζεστός
• feminine: ζεστή
• neuter: ζεστό

That is why the sentence says:

Το στήθος του είναι ζεστό.

not:

• ζεστός
• ζεστή

Είναι means is and comes from the verb είμαι = to be.

So the structure is straightforward:

• Το στήθος του = his chest
• είναι = is
• ζεστό = warm

Together:

Το στήθος του είναι ζεστό. = His chest is warm.

Unlike in some languages, in standard Greek you normally do include the verb είναι in a sentence like this.

Yes, Greek word order is more flexible than English, though the original order is the most neutral here.

Neutral order:

Το στήθος του είναι ζεστό.

You might also hear:

• Είναι ζεστό το στήθος του.
• Ζεστό είναι το στήθος του.

These alternatives can change the focus or emphasis, but not the core meaning.

For a learner, the safest default is the original pattern:

subject + είναι + adjective

Στήθος most often means chest, but depending on context it can also refer to the breast area more generally.

So its exact translation can depend on context:

• medical or physical description: chest
• emotional/literary style: sometimes breast or bosom

In your sentence, chest is the most natural translation.

This is a very common Greek habit. With body parts, Greek often prefers:

article + body part + possessive

Examples:

• Το χέρι μου πονάει. = My hand hurts.
• Τα μάτια του είναι κλειστά. = His eyes are closed.
• Το πρόσωπό της είναι κόκκινο. = Her face is red.

So Το στήθος του is a very natural Greek way to say his chest.

For English speakers, this can feel unusual at first, but it is one of the most useful patterns to get comfortable with.

A rough pronunciation is:

To STI-thos tou EE-ne ze-STO

A few helpful notes:

• σ τή θος: the θ sounds like th in think
• του sounds like too
• είναι is pronounced roughly EE-ne
• ζεστό has the stress on the last syllable: ze-STO

The written accent marks show you where the stress goes:

• στήθος
• είναι
• ζεστό

Yes. On its own, του can mean:

• his
• its
• of him
• of it

So without context, Το στήθος του could theoretically mean his chest or its chest.

In real life, context usually makes the meaning clear. If you are talking about a man or boy, it will normally be understood as his chest.

Yes, but that would usually add emphasis.

The ordinary, natural way is:

Το στήθος του είναι ζεστό.

If you wanted to emphasize possession, Greek can use stronger wording, for example with δικός in some contexts, but that is usually unnecessary here.

So for a simple statement, του is exactly the right choice. It sounds natural and idiomatic.