Στη μεγάλη διασταύρωση πρέπει να μπεις στη δεξιά λωρίδα, γιατί μετά είναι αργά.

Στη is the contracted form of σε τη(ν).

• σε = in / at / to
• τη(ν) = the feminine singular accusative article, the

So στη μεγάλη διασταύρωση means at the big intersection.

In modern Greek, this contraction is extremely common:

• σε + τη(ν) → στη(ν)
• σε + το → στο
• σε + τον → στον

Here, because μεγάλη starts with a consonant, στη is the normal form.

Both μεγάλη and διασταύρωση are feminine singular forms, and they agree with each other.

• η διασταύρωση = the intersection
• η μεγάλη διασταύρωση = the big intersection

After the preposition σε, Greek normally uses the accusative case, so the phrase is grammatically in the accusative. However, with many feminine nouns like διασταύρωση, the accusative singular looks the same as the nominative singular.

So although a learner may not see a visible change in the noun, the phrase is still functioning as an accusative phrase after σε.

Διασταύρωση means intersection or crossroads.

It comes from the idea of lines or roads crossing. In driving directions, it is a very common word.

Examples:

• Στη διασταύρωση στρίψε αριστερά. = At the intersection, turn left.
• Η μεγάλη διασταύρωση = the big intersection

Πρέπει να means must, have to, or need to.

• πρέπει = it is necessary / one must
• να introduces the verb that follows

So:

• πρέπει να μπεις = you must get into / you need to move into

In modern Greek, να is the normal particle used before subjunctive-style verb forms. After πρέπει, you normally use να + verb.

Compare:

• Πρέπει να φύγω. = I have to leave.
• Πρέπει να περιμένεις. = You have to wait.

Μπεις is the form used after να here, and it comes from the aorist stem of μπαίνω.

• dictionary form: μπαίνω = I enter / I get in
• aorist subjunctive: να μπω, να μπεις, να μπει...

So:

• πρέπει να μπεις = you must get into / move into

A learner often expects μπαίνεις, but μπαίνεις is an indicative present form meaning you enter / you are entering.

The reason Greek uses μπεις here is that this is a single, complete action: you need to get into the right lane at a particular moment. Greek often uses the aorist subjunctive for that kind of one-time action.

Very roughly:

• να μπεις = to get into, as one completed move
• να μπαίνεις = to be getting into / to keep entering / to enter habitually

In this sentence, the one-time action is what is needed.

Literally, it means enter the right lane.

In more natural English, especially for driving, it means:

• move into the right lane
• get into the right lane

Greek often uses μπαίνω in places where English uses go into, get into, or move into.

So να μπεις στη δεξιά λωρίδα is a very natural Greek way to say that you should position your car in the right lane.

Because λωρίδα is a feminine singular noun, the adjective must agree with it.

• η λωρίδα = the lane
• η δεξιά λωρίδα = the right lane

Agreement in Greek means the adjective matches the noun in:

• gender
• number
• case

Here both words are feminine singular.

Also, δεξιά can be either:

• an adjective: right
• an adverb: to the right

In this sentence, it is an adjective because it describes λωρίδα.

For the same reason as at the beginning: it is σε + τη(ν) contracted.

• στη μεγάλη διασταύρωση = at the big intersection
• στη δεξιά λωρίδα = into the right lane

The preposition σε is very flexible in Greek. Depending on context, it can mean:

• in
• at
• to
• into

Here:

• with διασταύρωση, it is location: at the intersection
• with λωρίδα, it suggests movement into that lane: into the right lane

Here γιατί means because.

Greek γιατί can mean both:

• why
• because

You tell which meaning it has from the sentence structure and context.

In this sentence:

• ..., γιατί μετά είναι αργά.
• ..., because later it is too late.

So it is clearly giving a reason, not asking a question.

Examples:

• Γιατί έφυγες; = Why did you leave?
• Έφυγα γιατί κουράστηκα. = I left because I got tired.

Word for word, it is:

• μετά = after / later / afterwards / then
• είναι = is
• αργά = late

So the literal sense is after that, it is late or later, it is late.

But in natural English, the meaning is:

• after that, it’s too late
• if you wait until later, it’s too late

This is a very common Greek way to warn someone that they need to act now, before the opportunity passes.

So the whole idea is: At the big intersection you need to get into the right lane, because after that it’s too late.

Greek often drops subject pronouns because the verb ending already shows the person.

Here, μπεις already tells you that the subject is you singular.

So Greek does not need to say εσύ unless it wants emphasis.

Compare:

• Πρέπει να μπεις... = You must get in...
• Εσύ πρέπει να μπεις... = You must get in... / You, specifically, must get in...

If the speaker were talking to more than one person, or using formal you, the form would be different:

• πρέπει να μπείτε = you must get in

Greek word order is flexible, and putting Στη μεγάλη διασταύρωση first gives the location immediate importance.

It sets the scene first:

• At the big intersection, you need to move into the right lane...

That sounds very natural in instructions and directions.

You could also hear a different order, such as:

• Πρέπει να μπεις στη δεξιά λωρίδα στη μεγάλη διασταύρωση...

But the original version is clearer and more natural for spoken directions, because it tells you exactly when/where the important action happens.

By itself, είναι αργά literally means it is late. But context often gives it the stronger meaning it is too late.

In this sentence, that is definitely the intended meaning. The speaker is warning that if you do not move into the right lane at that intersection, you will miss the chance later.

So although too is not separately stated in Greek, English normally translates it as:

• because after that it’s too late

This kind of context-based strengthening is very common in both Greek and English.