Μασάω αργά γιατί πονάει το δόντι μου.

Yes — that is a very common question.

Μασάω means I chew, and many modern Greek verbs of this type have two common present-tense forms:

• μασάω
• μασώ

Both are used and both are correct in Modern Greek. So:

• Μασάω αργά
• Μασώ αργά

both mean I chew slowly.

The -άω version often sounds a bit more full or slightly more conversational in some contexts, but in everyday Greek you will hear both patterns with many verbs:

• αγαπάω / αγαπώ
• ρωτάω / ρωτώ
• περνάω / περνώ

So here, Μασάω is just the 1st person singular present form: I chew.

Because αργά is an adverb, not an adjective.

• αργός / αργή / αργό = slow
• αργά = slowly

In the sentence, αργά describes how the action happens:

• Μασάω αργά = I chew slowly

Compare:

• Είναι αργός. = He is slow.
• Περπατά αργά. = He walks slowly.

So the sentence needs the adverb αργά.

Yes. Γιατί can mean both:

• because
• why

The meaning depends on context.

In your sentence:

• Μασάω αργά γιατί πονάει το δόντι μου.
• I chew slowly because my tooth hurts.

Here γιατί clearly introduces a reason, so it means because.

As a question word:

• Γιατί μασάς αργά;
• Why are you chewing slowly?

So the word is the same, but the sentence structure and punctuation make the meaning clear.

Πονάει is the 3rd person singular present form of πονάω / πονώ = to hurt, to ache.

So:

• πονάω = I hurt / I am hurting
• πονάς = you hurt
• πονάει = it hurts / he hurts / she hurts

In this sentence, the subject is:

• το δόντι μου = my tooth

Since το δόντι μου is singular, the verb is singular too:

• το δόντι μου πονάει
• my tooth hurts

Greek very often uses this structure with body parts and pain.

Also, like μασάω, this verb has variant forms:

• πονάω / πονώ
• πονάει / πονά

So you may also see:

• πονά το δόντι μου

Because the grammatical subject is το δόντι μου = my tooth, which is singular.

So Greek matches the verb to δόντι:

• το δόντι μου πονάει = my tooth hurts

If it were plural, the verb would also be plural:

• Τα δόντια μου πονάνε.
• My teeth hurt.

So the key is:

• δόντι = singular
• δόντια = plural

Because that is the normal Greek way to express possession with words like μου (my), σου (your), του/της (his/her), etc.

Greek usually says:

• το δόντι μου = my tooth
• το σπίτι μου = my house
• η αδερφή μου = my sister

So unlike English, Greek typically uses:

• article + noun + possessive pronoun

rather than putting my before the noun.

This is completely standard Greek.

Usually, yes.

In standard Modern Greek, when you use a possessive pronoun like μου, you normally also use the definite article:

• το βιβλίο μου = my book
• η τσάντα μου = my bag
• ο φίλος μου = my friend

So το δόντι μου is the expected form.

English says my tooth with no article, but Greek normally wants the article.

Because Greek is a pro-drop language, which means subject pronouns are often omitted when the verb ending already shows who the subject is.

• Μασάω already means I chew
• so εγώ is not necessary

You could say:

• Εγώ μασάω αργά...

but that would usually add emphasis, like:

• I chew slowly...
• As for me, I chew slowly...

In neutral speech, the pronoun is usually left out.

Yes, Greek word order is more flexible than English.

Both of these are possible:

• Πονάει το δόντι μου
• Το δόντι μου πονάει

Both mean my tooth hurts.

The version in your sentence,

• γιατί πονάει το δόντι μου,

sounds natural and conversational. Putting the verb first can make the statement flow nicely after γιατί.

But γιατί το δόντι μου πονάει is also understandable and possible, depending on rhythm or emphasis.

Yes.

The Greek present tense often covers both:

• a general/habitual meaning
• a current, ongoing meaning

So Μασάω αργά can mean:

• I chew slowly
• I’m chewing slowly

Context tells you which one is meant.

In this sentence, because of the immediate reason γιατί πονάει το δόντι μου, many speakers would naturally understand it as something happening right now, but the Greek form itself can cover both meanings.

Yes, that is also possible.

You may hear:

• Πονάει το δόντι μου.
• Με πονάει το δόντι μου.

Both can mean something like my tooth hurts.

The version with με literally includes me:

• It hurts me, my tooth

In real usage, both are common, and the difference is often small. The version Πονάει το δόντι μου is very natural and straightforward.

So the sentence you were given is perfectly idiomatic.

A simple learner-friendly pronunciation guide:

• πονάει ≈ po-NA-ee
• δόντι ≈ THON-dee
  (with Greek δ pronounced like the th in this, not like English d)

A few helpful points:

• The stress in πονάει is on νά
• The stress in δόντι is on δό
• Greek αι in πονάει here is part of the verb ending and is pronounced like e/ee in modern speech, so the whole word flows as three syllables for many learners: po-NA-i

If you want a very rough full pronunciation:

• Μασάω αργά γιατί πονάει το δόντι μου
• ≈ ma-SA-o ar-GHA ya-TI po-NA-i to THON-dee moo

In Greek, punctuation before γιατί is not always handled exactly the same way learners might expect from English.

In a short sentence like this:

• Μασάω αργά γιατί πονάει το δόντι μου.

it is very normal to write it without a comma.

Greek punctuation tends to be somewhat lighter in many everyday sentences of this kind. So the sentence as written looks natural.

It sounds natural.

A Greek speaker could absolutely say:

• Μασάω αργά γιατί πονάει το δόντι μου.

It is simple, clear, and idiomatic.

You might also hear close alternatives such as:

• Μασάω σιγά-σιγά γιατί πονάει το δόντι μου. = I’m chewing little by little / very slowly because my tooth hurts.
• Δεν μπορώ να μασήσω καλά γιατί πονάει το δόντι μου. = I can’t chew well because my tooth hurts.

But the original sentence is perfectly normal Greek.