Αν δεν βρω ψωμί στο παντοπωλείο, θα πάω στο σούπερ μάρκετ.

Αν means if. It introduces the condition:

• Αν δεν βρω ψωμί στο παντοπωλείο = If I don’t find bread at the grocery store

This is a very common way to make if-sentences in Greek.

After αν in a sentence like this, Greek often uses the perfective non-past form of the verb, which here is βρω from βρίσκω (to find).

So:

• βρίσκω = I find / I am finding
• βρω = find, as a single complete event, in a context like if, when, etc.

In this sentence, βρω means something like:

• if I happen to find
• if I find

You do not normally say αν θα βρω here. Greek usually avoids θα after αν in this kind of condition.

Βρω is the perfective non-past form of βρίσκω.

English does not have a direct equivalent, so it can feel unfamiliar. In this sentence it is used because the speaker is talking about one complete future action:

• If I don’t find bread...

The idea is not finding in general or being in the process of finding, but succeeding in finding it or not.

In this sentence, Greek uses δεν:

• Αν δεν βρω...

That is the normal choice after αν in a condition like this.

A learner may expect μη(ν) because forms like βρω can look similar to forms used with να, but with αν the usual negation here is δεν, not μην.

So:

• Αν δεν βρω... = If I don’t find...

Θα is the usual future marker in Modern Greek.

• πάω = I go / I am going
• θα πάω = I will go

So:

• θα πάω στο σούπερ μάρκετ = I will go to the supermarket

This is the result part of the condition:

• If I don’t find bread..., I will go...

Both πάω and πηγαίνω can mean I go.

In everyday Greek, πάω is extremely common and natural, especially in speech.

So:

• θα πάω = very common way to say I will go
• θα πηγαίνω would usually mean something more like I will be going / I will go regularly, so it would not fit as well here

For a single future trip to the supermarket, θα πάω is the natural choice.

Στο is a contraction of:

• σε + το = στο

It means to the, at the, or in the, depending on context.

So:

• στο παντοπωλείο = at/to the grocery store
• στο σούπερ μάρκετ = to the supermarket

In this sentence:

• βρω ψωμί στο παντοπωλείο = find bread at the grocery store
• πάω στο σούπερ μάρκετ = go to the supermarket

Because σε takes the accusative case, and these nouns are being used with the neuter singular article το.

For neuter nouns like these, the nominative and accusative are often the same in form:

• το παντοπωλείο
• το σούπερ μάρκετ

After σε, you get:

• στο παντοπωλείο
• στο σούπερ μάρκετ

So even though there is a case change grammatically, the noun itself may not visibly change.

Greek often leaves out the article when talking about something in a general or indefinite way.

So:

• βρω ψωμί = find bread

This sounds natural when the meaning is some bread / bread in general.

If you added an article, the meaning could become more specific depending on context.

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

This sentence begins with the condition:

• Αν δεν βρω ψωμί στο παντοπωλείο, θα πάω στο σούπερ μάρκετ.

But you could also say:

• Θα πάω στο σούπερ μάρκετ αν δεν βρω ψωμί στο παντοπωλείο.

Both are natural. The version with the αν-clause first puts more emphasis on the condition.

Because the sentence starts with the if-clause:

• Αν δεν βρω ψωμί στο παντοπωλείο, ...

The comma separates the condition from the main clause:

• ..., θα πάω στο σούπερ μάρκετ.

This is similar to English, where a comma is also common when the if-part comes first.

They are both places where you can buy food, but they are not exactly the same idea.

• παντοπωλείο = a grocery shop / small food store / traditional provisions shop
• σούπερ μάρκετ = supermarket

So the sentence suggests:

• If I can’t find bread in the smaller grocery-type shop, I’ll go to the supermarket.

It is a real, open possibility: the speaker genuinely means this may happen.

• If I don’t find bread at the grocery store, I’ll go to the supermarket.

Greek commonly expresses this kind of future condition with:

• αν + perfective non-past
• main clause with θα

That pattern is exactly what you see here:

• Αν δεν βρω..., θα πάω...

This sentence is about one future situation.

If the speaker meant something habitual, Greek would usually choose different forms, often with the imperfective:

• Αν δεν βρίσκω ψωμί στο παντοπωλείο, πηγαίνω στο σούπερ μάρκετ.

That would mean something like:

• If I don’t find bread at the grocery store, I go to the supermarket.
• or Whenever I don’t find bread..., I go...

So βρω / θα πάω helps show that this sentence is about a single future case, not a repeated routine.