Ο θαυμαστής χαμογελάει.

ο is the masculine singular definite article, so here it means the.

It appears because θαυμαστής is:

• masculine
• singular
• in the nominative case because it is the subject of the sentence

So ο θαυμαστής means the admirer / the fan.

It is in the nominative singular.

You can tell because:

• it is the subject of the sentence
• it comes with the nominative masculine singular article ο
• the dictionary form of this noun is θαυμαστής

In this sentence, θαυμαστής is the person doing the action.

Yes, θαυμαστής is a masculine noun.

A common feminine form is θαυμάστρια.

So:

• ο θαυμαστής = a male admirer / fan
• η θαυμάστρια = a female admirer / fan

Greek nouns and articles usually show gender much more clearly than English does.

χαμογελάει is the 3rd person singular present tense form of the verb χαμογελάω / χαμογελώ, meaning to smile.

So it matches a subject like:

• he
• she
• it
• or a singular noun such as ο θαυμαστής

That is why ο θαυμαστής χαμογελάει is grammatically parallel to the admirer smiles.

It can mean either one, depending on context.

In Modern Greek, the present tense often covers both:

• simple present: smiles
• present progressive: is smiling

So without more context, χαμογελάει could naturally be understood as either:

• smiles
• is smiling

This is very normal in Greek.

Both can be correct.

For many verbs of this type, especially verbs in -άω / -ώ, the 3rd person singular can appear as:

• χαμογελάει
• χαμογελά

These are both standard in everyday Modern Greek, though style and preference can vary a bit.

So:

• Ο θαυμαστής χαμογελάει.
• Ο θαυμαστής χαμογελά.

Both are fine.

A rough English-friendly guide would be:

o tha-vma-STIS ha-mo-ye-LA-i

A few useful details:

• ο sounds like o
• θ sounds like th in think
• αυ in θαυμαστής is pronounced av here, because it comes before a voiced sound
• χ is not the English h; it is a rough sound like German Bach or Scottish loch
• γ before ε in γε sounds somewhat like y
• the stress falls on:
  • -στής in θαυμαστής
  • -λά- in χαμογελάει

So the two strongly stressed parts are -στής and -λά-.

In Modern Greek, the letter combination αυ is not always pronounced like a simple vowel combination.

It is pronounced:

• av before a voiced sound
• af before a voiceless sound

In θαυμαστής, the next sound is μ, which is voiced, so αυ becomes av.

That is why θαυμαστής sounds roughly like thavmastís, not thaumastís.

Yes. Greek word order is more flexible than English word order.

So both of these are possible:

• Ο θαυμαστής χαμογελάει.
• Χαμογελάει ο θαυμαστής.

The basic meaning stays the same, but the emphasis can shift a little.

Very roughly:

• Ο θαυμαστής χαμογελάει = a neutral statement
• Χαμογελάει ο θαυμαστής = slightly more focus on the action or a more context-driven word order

English usually needs a more fixed order, but Greek does not.

In normal everyday Greek, that would usually sound unnatural if you mean the admirer / the fan.

Greek uses the definite article much more often than English. So with a specific person, ο θαυμαστής is the natural form.

Without the article, θαυμαστής may sound:

• incomplete
• unnatural in ordinary speech
• or like a special style such as a headline, label, or very compressed wording

So for a normal sentence, keep ο.

Because Greek often does not need subject pronouns.

The verb ending already tells you the person and number:

• χαμογελάει = he/she/it smiles or is smiling

And in this sentence, the subject is already explicitly stated as ο θαυμαστής, so a pronoun would be unnecessary.

Greek commonly omits pronouns unless there is a reason to add emphasis or contrast.

So:

• Ο θαυμαστής χαμογελάει. = perfectly natural
• adding αυτός would usually add emphasis, not just basic grammar