Ο κουμπάρος γελάει και λέει ότι ο γαμπρός θα αργήσει, γιατί ακόμα δεν ξέρει ποια γραβάτα ταιριάζει με το κοστούμι.

In this sentence, ο κουμπάρος most naturally means the best man or the wedding sponsor.

That word can have a few related meanings in Greek depending on context, such as:

• best man at a wedding
• godfather
• a ritual sponsor in church contexts

Because the sentence also has ο γαμπρός (the groom) and talks about a tie and a suit, the wedding meaning is clearly the right one here.

Greek uses the definite article very often, much more regularly than English.

Here:

• ο κουμπάρος = the best man
• ο γαμπρός = the groom
• το κοστούμι = the suit

The articles also show gender:

• ο = masculine
• η = feminine
• το = neuter

So:

• κουμπάρος is masculine
• γαμπρός is masculine
• κοστούμι is neuter

They are in the present tense, third person singular, because the subject is singular: ο κουμπάρος.

So:

• γελάει = he laughs / is laughing
• λέει = he says / is saying

Greek present tense often covers both the English simple present and present continuous, depending on context.

Also, these two forms are very common in everyday Greek:

• γελάει can also appear as γελά
• λέει is the normal form of he says

ότι means that and introduces a reported statement.

So:

• λέει ότι... = he says that...

This is very common after verbs of saying, knowing, thinking, hearing, etc.

For example:

• λέω ότι... = I say that...
• νομίζω ότι... = I think that...

You may also see πως used in similar situations:

• λέει πως... = he says that...

This is a very common learner question.

• ότι = that
• ό,τι = whatever / anything that

In your sentence, it is ότι because it introduces a statement:

• λέει ότι ο γαμπρός θα αργήσει
• he says that the groom will be late

By contrast:

• Πάρε ό,τι θέλεις = Take whatever you want

The comma in ό,τι helps distinguish it in writing.

θα αργήσει is the normal future form here: he will be late / he will arrive late.

In Modern Greek, θα is used for the future, and it is usually followed by a special verb form often called the subjunctive form or non-past dependent form. With many verbs, this looks like the aorist-based form.

So:

• αργεί = he is late / he is being late / he tends to be late
• θα αργήσει = he will be late

In this sentence, the best man is saying something about what will happen, so the future is needed.

Here αργήσει means something like:

• be late
• arrive late
• take longer than expected

So ο γαμπρός θα αργήσει means:

• the groom will be late

It does not necessarily mean he is slow in general. It means he will not be ready or arrive on time.

γιατί here means because and introduces the reason:

• ...θα αργήσει, γιατί ακόμα δεν ξέρει...
• ...he will be late, because he still doesn’t know...

A useful thing to remember is that γιατί can mean both:

• because
• why

The meaning depends on the sentence:

• Γιατί άργησε; = Why was he late?
• Άργησε γιατί είχε κίνηση. = He was late because there was traffic.

ακόμα here means still or yet, depending on how you translate it in English.

• ακόμα δεν ξέρει = he still doesn’t know / he doesn’t know yet

Word order in Greek is flexible, but putting ακόμα before the negative is very natural here and emphasizes the continuing situation.

You could also hear:

• δεν ξέρει ακόμα

Both are possible, though the nuance may shift slightly depending on emphasis.

Because the sentence mixes:

• a future event: the groom will be late
• a present reason: he still doesn’t know which tie matches the suit

So the logic is:

• future result: θα αργήσει
• present cause: δεν ξέρει

In other words, he will be late because right now he still doesn’t know.

That is completely normal in both Greek and English.

ποια means which and agrees with γραβάτα.

Since γραβάτα is:

• feminine
• singular

the form is:

• ποια γραβάτα = which tie

This introduces an indirect question:

• δεν ξέρει ποια γραβάτα ταιριάζει...
• he doesn’t know which tie matches...

In the larger sentence, the whole clause ποια γραβάτα ταιριάζει με το κοστούμι is what he doesn’t know.

Inside that clause, ποια γραβάτα is the subject of ταιριάζει.

So the structure is:

• δεν ξέρει = he doesn’t know
• [ποια γραβάτα ταιριάζει με το κοστούμι] = which tie matches the suit

Within that bracketed clause:

• ποια γραβάτα = subject
• ταιριάζει = verb

ταιριάζει means matches, goes well with, or suits.

Here:

• ποια γραβάτα ταιριάζει με το κοστούμι
• which tie matches the suit

A very common pattern is:

• ταιριάζω με + accusative
• match / go with

Examples:

• Αυτά τα παπούτσια ταιριάζουν με το φόρεμα.
• These shoes go with the dress.

So in your sentence:

• με το κοστούμι = with the suit

Because με normally takes the accusative in Modern Greek.

So:

• με το κοστούμι = with the suit

Since κοστούμι is a neuter noun, the nominative and accusative singular look the same:

• nominative: το κοστούμι
• accusative: το κοστούμι

That is why the form does not visibly change here.

In this sentence, ο γαμπρός clearly means the groom.

But γαμπρός can also mean:

• bridegroom
• son-in-law, depending on context

Here the wedding context makes groom the correct meaning.

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

The given sentence is natural and clear, but Greek often moves words around for emphasis. For example, parts like ακόμα, ο γαμπρός, or με το κοστούμι could shift position in other versions.

Still, the original version is very standard:

• Ο κουμπάρος γελάει και λέει ότι ο γαμπρός θα αργήσει, γιατί ακόμα δεν ξέρει ποια γραβάτα ταιριάζει με το κοστούμι.

It sounds like normal spoken or written Greek.