Η προπληρωμένη κάρτα λειτουργεί.

In Greek, Η here is the feminine singular definite article, meaning the.

A few useful things to know:

• It is pronounced ee, not like English h.
• At the start of the sentence it is capitalized, so you see Η instead of η.
• Greek Η/η is also the letter eta, so learners often do a double take when they first see it.

So Η προπληρωμένη κάρτα = the prepaid card.

Because κάρτα is a feminine singular noun, and Greek articles must agree with the noun in gender, number, and case.

Here are the singular definite articles in the nominative:

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

Since κάρτα is feminine, Greek uses η.

Προπληρωμένη is an adjective meaning prepaid.

It comes from the idea of paid in advance:

• προ- = before, in advance
• related to πληρώνω = to pay

In this sentence, προπληρωμένη agrees with κάρτα:

• feminine
• singular
• nominative

So:

• η προπληρωμένη κάρτα = the prepaid card

You can think of it as the Greek equivalent of an adjective, even though historically it is built from a participial form.

It ends in -η because it is matching the noun κάρτα, which is:

• feminine
• singular
• nominative

Greek adjectives change form to match the noun they describe.

So if the noun changed, the adjective would change too. For example:

• η προπληρωμένη κάρτα = the prepaid card
• το προπληρωμένο εισιτήριο = the prepaid ticket
• ο προπληρωμένος λογαριασμός = the prepaid bill/account

This agreement is a very important feature of Greek grammar.

Λειτουργεί is:

• present tense
• 3rd person singular
• from λειτουργώ = to function, operate

So it means:

• it works
• it is working
• it functions

Because the subject is η προπληρωμένη κάρτα (the prepaid card), the singular verb form is used.

Both can often be translated as works, but they are not always identical in tone.

• λειτουργεί = functions / operates
• δουλεύει = works, often more conversational

With machines, systems, devices, cards, or services, λειτουργεί often sounds a bit more precise or formal.

So for a card, terminal, app, or machine, λειτουργεί is very natural.

A simple pronunciation guide is:

ee pro-plee-ro-ME-nee KAR-ta lee-toor-YEE

A few notes:

• Η = ee
• προπληρωμένη has the stress on -μέ-
• κάρτα has the stress on κάρ-
• λειτουργεί has the stress on the last syllable

The γ in λειτουργεί is not a hard English g. Before ει, it sounds softer, roughly like a y sound for many learners' ears.

The noun phrase η προπληρωμένη κάρτα is in the nominative case because it is the subject of the sentence.

So:

• η = nominative feminine singular article
• προπληρωμένη = nominative feminine singular adjective
• κάρτα = nominative feminine singular noun

The verb λειτουργεί does not have case, because verbs do not change for case.

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

The neutral statement is:

• Η προπληρωμένη κάρτα λειτουργεί.

But Greek can move things around for emphasis. For example:

• Λειτουργεί η προπληρωμένη κάρτα.

That could sound like The prepaid card works or The prepaid card is working, with a slightly different emphasis depending on context.

Even though word order can move, the basic sentence here is simple and natural.

In normal Greek, η is the natural choice here if you mean the prepaid card.

Without the article, Προπληρωμένη κάρτα λειτουργεί sounds incomplete or unnatural in most ordinary contexts. Greek uses the definite article more regularly than English does.

So:

• Η προπληρωμένη κάρτα λειτουργεί. = The prepaid card works.

If you wanted a prepaid card, you would normally say:

• Μια προπληρωμένη κάρτα λειτουργεί.

Yes. The Greek present tense often covers both ideas:

• The prepaid card works
• The prepaid card is working

Which one sounds better in English depends on context.

For example:

• if you are talking about general functionality, works is natural
• if you are reacting to a situation right now, is working may be more natural

Greek λειτουργεί can cover both.

In the plural, both the article/adjective and the verb would change:

• Οι προπληρωμένες κάρτες λειτουργούν.
  = The prepaid cards work.

Changes to notice:

• η → οι
• προπληρωμένη → προπληρωμένες
• κάρτα → κάρτες
• λειτουργεί → λειτουργούν

This is a good example of how Greek shows agreement in several parts of the sentence.