Ο παλαιοπώλης είναι στο παλαιοπωλείο, στο παζάρι.

They are related, but they mean different things:

• παλαιοπώλης = the antique dealer / second-hand dealer (a person)
• παλαιοπωλείο = the antique shop / second-hand shop (a place)

This is a very common pattern in Greek:

• a word for a person
• a related word for the place connected with that person or job

Here:

• -πώλης means seller / dealer
• -πωλείο means shop / store

So the sentence uses both:

• the person: Ο παλαιοπώλης
• the place: στο παλαιοπωλείο

Ο is the masculine singular definite article, meaning the.

So:

• Ο παλαιοπώλης = the antique dealer

Greek uses the definite article more often than English, especially with subject nouns. So even where English might sometimes say just Antique dealer is... in certain contexts, Greek normally wants Ο παλαιοπώλης.

στο is the contracted form of:

• σε = in / at / to
• το = the

So:

• σε το → στο

This contraction is standard and very common in modern Greek.

Examples:

• στο σπίτι = in the house
• στο σχολείο = at school
• στο παλαιοπωλείο = in/at the antique shop

Because Greek repeats the preposition with each location phrase.

So the sentence literally has:

• in the antique shop
• in the bazaar

This can sound like:

• The antique dealer is in the antique shop, at the bazaar.

The second phrase, στο παζάρι, gives extra location information. It tells you where the shop is, or places the whole situation more specifically.

Greek often repeats the preposition instead of leaving it implied.

After σε (and therefore after στο), Greek normally uses the accusative case.

So in this sentence:

• το παλαιοπωλείο is accusative
• το παζάρι is accusative

However, both of these nouns are neuter, and in the singular their nominative and accusative forms are the same. So you do not see a change in the noun itself.

That is why:

• nominative: το παλαιοπωλείο
• accusative: το παλαιοπωλείο

and

• nominative: το παζάρι
• accusative: το παζάρι

Because the sentence is talking about the place, not the person, after στο.

Compare:

• Ο παλαιοπώλης = the antique dealer (person)
• στο παλαιοπωλείο = in the antique shop (place)

Also, the forms of the are different because the nouns have different genders:

• παλαιοπώλης is masculine → ο
• παλαιοπωλείο is neuter → το, so with σε it becomes στο

If you were saying to the antique dealer, then you would use a masculine form:

• στον παλαιοπώλη

But that is not what this sentence says.

είναι means is.

It is the 3rd person singular form of the verb είμαι = to be.

So:

• Ο παλαιοπώλης είναι... = The antique dealer is...

Greek does not need a separate word for he here, because the verb form already tells you the person and number.

Greek often leaves out subject pronouns when they are not needed. This is because the verb ending usually makes the subject clear.

So:

• είναι already means he/she/it is

Since the noun Ο παλαιοπώλης is already stated, there is no need to add he.

This is very normal in Greek.

The comma adds an extra piece of location information.

The structure is roughly:

• He is in the antique shop, at the bazaar.

So στο παζάρι is like an additional locator:

• the shop is at the bazaar
• or the whole scene is situated at the bazaar/market

It is not changing the main grammar of the sentence; it is just adding more detail.

Not always exactly, but it is often translated as bazaar or market.

Depending on context, παζάρι can suggest:

• an open-air market
• a bazaar
• a fair-like market setting
• sometimes even bargaining/haggling in other contexts

In this sentence, it refers to a market/bazaar location.

A helpful approximate pronunciation is:

• παλαιοπώλης ≈ pa-lay-o-PO-lis
• παλαιοπωλείο ≈ pa-lay-o-po-LEE-o
• παζάρι ≈ pa-ZA-ri

A few things to notice:

• αι is pronounced like e in modern Greek
• the written accents show the stressed syllable:
  • παλαιοπώλης
  • παλαιοπωλείο
  • παζάρι

Stress is important in Greek, so it is worth paying attention to the accent marks.

Yes. παλαιο- comes from a word meaning old or ancient.

So these compounds are built from meaningful parts:

• παλαιο- = old / antique
• πώλης = seller
• πωλείο = shop

That is why:

• παλαιοπώλης = seller of old/antique things
• παλαιοπωλείο = shop for old/antique things

Greek often forms words this way, so learning to spot the parts of compound words can be very helpful.

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

The neutral, straightforward version here is:

• Ο παλαιοπώλης είναι στο παλαιοπωλείο, στο παζάρι.

But Greek can move things around for emphasis. For example, a speaker might front a location phrase in another context. Even so, the version you have is the most natural basic order for a simple statement:

• subject + verb + location

So for a learner, this sentence is a good model to follow.