Learn Hardcore Greek: Εδώ επιτρέπεται να πληρώσεις με κάρτα ή με μετρητά. - Here you are allowed to pay with a card or with cash.

the 3rd person singular, present tense, passive form of the verb επιτρέπω (I allow / I permit).
Literally it means it is allowed or is permitted.

So Εδώ επιτρέπεται… literally corresponds to Here it is allowed…, just like English uses an impersonal it in It is allowed to pay here. Greek simply drops the it and uses the passive verb alone.

If επιτρέπεται already means it is allowed, why do we need να πληρώσεις after it?

Επιτρέπεται by itself only says something is allowed, but not what:

Εδώ επιτρέπεται… = Here it is allowed… (but what is allowed?)

The part να πληρώσεις (to pay) tells you what action is allowed.
Greek normally expresses to do something after verbs like επιτρέπεται, πρέπει, θέλω, etc., using:

να + subjunctive verb

So:

επιτρέπεται = it is allowed
να πληρώσεις = to pay (you pay)
επιτρέπεται να πληρώσεις = it is allowed (for you) to pay

What exactly is να πληρώσεις? What is να, and what form is πληρώσεις?

Να πληρώσεις is a subjunctive verb phrase:

να: a particle that introduces the subjunctive mood (it often corresponds to to, that, or (so that) you … in English).
πληρώσεις: 2nd person singular, aorist subjunctive of πληρώνω (I pay).

Basic forms of the verb:

present: πληρώνω (I pay / I am paying)
aorist (simple past): πλήρωσα (I paid)
aorist subjunctive 2nd sg: να πληρώσεις (that you pay / for you to pay)

Greek has no real infinitive like English to pay. Instead it uses να + subjunctive to express that idea. So να πληρώσεις is the natural way to say to pay (you) in this kind of sentence.

Why is it πληρώσεις and not πληρώνεις after να? What is the difference?

Both να πληρώσεις and να πληρώνεις are possible Greek forms, but they differ in aspect (how the action is viewed):

να πληρώσεις – aorist (perfective) subjunctive
- Focus on the whole action as a single, complete event.
- Here: to pay (once, complete the payment).
να πληρώνεις – present (imperfective) subjunctive
- Focus on ongoing, repeated, or habitual action.
- More like to be paying / to keep paying / to pay regularly.

In the sentence:

Εδώ επιτρέπεται να πληρώσεις με κάρτα ή με μετρητά.

the situation is a single transaction: you complete one payment. That’s why the aorist subjunctive (να πληρώσεις) is natural.
Να πληρώνεις would sound more like Here it is allowed that you (regularly / habitually) pay…, which doesn’t really fit a one‑off payment.

Is πληρώσεις talking to one person or more than one person? How would you make it plural or more polite?

Πληρώσεις is:

2nd person singular, informal you – talking to one person in a familiar way.

To address more than one person or to be polite/formal, you use the 2nd person plural subjunctive:

να πληρώσετε

So you could say:

Εδώ επιτρέπεται να πληρώσεις με κάρτα ή με μετρητά.
– informal, you (one person)
Εδώ επιτρέπεται να πληρώσετε με κάρτα ή με μετρητά.
– plural or polite you

On a sign or in public notices, you are much more likely to see the plural/polite form (να πληρώσετε / να πληρώνετε) rather than να πληρώσεις.

What is the grammatical subject of επιτρέπεται here? Is εδώ the subject?

Εδώ is not the subject. It’s an adverb of place meaning here.

In this sentence, επιτρέπεται is used impersonally:

There is no real subject in Greek.
It corresponds to English It is allowed… where it is just a dummy subject.

So structurally, Greek has:

Εδώ (here, adverb of place)
επιτρέπεται (is allowed, impersonal passive verb)
να πληρώσεις… (what is allowed)

You could think of it as: Here, it is allowed (for you) to pay…, but Greek doesn’t need an it.

Could we say Εδώ μπορείς να πληρώσεις με κάρτα ή με μετρητά instead? What is the difference between επιτρέπεται and μπορείς?

Yes, you can also say:

Εδώ μπορείς να πληρώσεις με κάρτα ή με μετρητά.

The difference is mainly in style and nuance:

επιτρέπεται
- impersonal, more formal / rule‑like
- emphasizes permission according to rules or policy
- typical for signs, regulations, announcements
μπορείς (you can / you are able to)
- personal, 2nd person singular
- can mean you are allowed to, but also you are able to / it’s possible for you
- often more colloquial / conversational

So:

Εδώ επιτρέπεται να πληρώσεις…
– more like Here it is permitted to pay… (focus on permission as a rule).
Εδώ μπορείς να πληρώσεις…
– more like Here you can pay… (you have the option / it’s possible & allowed).

Why do we say με κάρτα and not με την κάρτα? When is the article dropped?

Με κάρτα literally means with card, and in Greek this often omits the article when we talk about a means or method in a general way:

με κάρτα = by card / with a card (as a method of payment)
με μετρητά = in cash / with cash

We normally drop the article when a noun is used:

in a general, non‑specific sense
as a means of transport or payment, or another kind of instrument

Examples:

Πήγα με λεωφορείο. – I went by bus.
Πλήρωσα με κάρτα. – I paid by card.

If you say με την κάρτα, you usually mean a specific card already known in context:

Πλήρωσε με την κάρτα της γυναίκας του.
– He paid with his wife’s card (a specific card).

So in your sentence, because we are talking about the method of payment in general, με κάρτα is correct and natural.

What does the preposition με do here? Does it always translate as with?

Με is a very common preposition. Its core meanings are:

with (together with someone/something)
with / by (indicating a tool, instrument, or means)

In your sentence:

με κάρτα = with a card / by card (means of payment)
με μετρητά = with cash / in cash

Other examples:

Πηγαίνω στη δουλειά με το αυτοκίνητο. – I go to work by car.
Κόβω το ψωμί με μαχαίρι. – I cut the bread with a knife.

So yes, με often translates as with, but in English we sometimes say by (by car, by card) where Greek still uses με.

What exactly are μετρητά? Are they singular or plural, and do they take an article?

Μετρητά means cash (physical money, notes and coins). Grammatically:

It is a neuter plural form (from an adjective meaning paid / countable).
It is normally used only in the plural: μετρητό in the singular is not used in this sense.

About the article:

Without article: με μετρητά
- general, non‑specific cash as a means of payment.
- like English in cash.
With article: τα μετρητά
- the cash (definite, specific amount of cash).
- e.g. Δεν έχω τα μετρητά μαζί μου. – I don’t have the cash with me.

In your sentence, since we are talking about the payment method in general, με μετρητά (no article) is the natural choice.

Can we change the word order, for example to Εδώ επιτρέπεται να πληρώσεις με μετρητά ή με κάρτα or Επιτρέπεται εδώ να πληρώσεις…? Does it change the meaning?

Greek word order is fairly flexible, so these are all grammatically possible:

Εδώ επιτρέπεται να πληρώσεις με κάρτα ή με μετρητά.
Εδώ επιτρέπεται να πληρώσεις με μετρητά ή με κάρτα.
Επιτρέπεται εδώ να πληρώσεις με κάρτα ή με μετρητά.

The meaning stays the same; differences are mainly in naturalness and emphasis:

Starting with Εδώ is very natural when you are saying what is allowed in this place:
- Εδώ επιτρέπεται… = Here it is allowed…
Moving εδώ after επιτρέπεται (Επιτρέπεται εδώ…) is still correct, but it can sound a bit more formal or marked, and is less common in everyday speech for this specific kind of sentence.

Switching the order of με κάρτα and με μετρητά just changes which option you happen to mention first; it doesn’t affect the meaning.