Το ντουλαπάκι στα αποδυτήρια είναι κλειστό, αλλά έχω το κλειδί.

Ντουλαπάκι is the diminutive form of ντουλάπι. In everyday Greek, diminutives are very common and often do not always sound especially “small” in the literal sense. Here, ντουλαπάκι is the usual word for a locker or small cabinet/compartment.

So:

• το ντουλάπι = cabinet, cupboard
• το ντουλαπάκι = little cabinet, small compartment, locker

In places like gyms, swimming pools, or changing rooms, ντουλαπάκι is a very natural word.

Το is the neuter singular definite article, meaning the.

Greek articles change depending on:

• gender
• number
• case

Here, ντουλαπάκι is:

• neuter
• singular
• the subject of the sentence

So it takes το.

A few related forms:

• το ντουλαπάκι = the locker
• του ντουλαπακίου = of the locker
• τα ντουλαπάκια = the lockers

Στα is a contraction of σε + τα.

So:

• σε = in, at, to
• τα = the
• στα = in the / at the / to the

Αποδυτήρια means changing rooms / locker rooms, and it is plural in Greek.

So:

• στα αποδυτήρια = in the changing rooms / in the locker room area

This is very common in Greek:

• στο = σε + το
• στη / στην = σε + τη(ν)
• στα = σε + τα
• στους = σε + τους
• στις = σε + τις

Greek often uses the plural for places that English may also treat as plural, such as changing rooms. The word αποδυτήριο exists as singular, but αποδυτήρια is very common when talking about the whole area or facility.

So:

• το αποδυτήριο = the changing room / locker room
• τα αποδυτήρια = the changing rooms / locker rooms

In this sentence, στα αποδυτήρια refers to the place where the locker is located.

Κλειστό is the adjective meaning closed or locked/shut, depending on context.

So:

• είναι κλειστό = it is closed / locked

This is the normal, natural way to describe the state of something like a door, shop, locker, or box.

Κλεισμένο comes from the participle and can appear in some contexts, but for a simple description of state, κλειστό is the usual choice.

Examples:

• Η πόρτα είναι κλειστή. = The door is closed.
• Το μαγαζί είναι κλειστό. = The shop is closed.
• Το ντουλαπάκι είναι κλειστό. = The locker is closed/locked.

Because it agrees with το ντουλαπάκι, which is neuter singular.

Greek adjectives must agree with the noun they describe in:

• gender
• number
• case

Here:

• ντουλαπάκι = neuter singular
• so the adjective is κλειστό = neuter singular

Compare:

• ο χώρος είναι κλειστός = the area is closed (masculine)
• η πόρτα είναι κλειστή = the door is closed (feminine)
• το ντουλαπάκι είναι κλειστό = the locker is closed (neuter)

Greek often leaves out subject pronouns because the verb ending already shows who the subject is.

Έχω means I have, so the I is already built into the verb form.

That means:

• έχω = I have
• έχεις = you have
• έχει = he/she/it has

You could say εγώ έχω, but that usually adds emphasis, as in:

• αλλά εγώ έχω το κλειδί = but I have the key

Without εγώ, the sentence is more neutral and natural.

Αλλά means but.

It connects two contrasting ideas:

• Το ντουλαπάκι ... είναι κλειστό = The locker is locked/closed
• έχω το κλειδί = I have the key

So together:

• ..., αλλά έχω το κλειδί. = ..., but I have the key.

Its placement is very similar to English but: it usually comes between the two clauses.

Greek uses the definite article very often, often more often than English.

Το κλειδί means the key. In this sentence, it refers to a specific key: the key to that locker.

Using the article sounds natural because the key is identifiable from context.

Compare:

• έχω το κλειδί = I have the key
• έχω ένα κλειδί = I have a key

The first suggests the relevant key, the one needed here.

It is in the accusative case, because it is the direct object of έχω.

You can ask:

• What do I have?
• the key

So:

• έχω = I have
• το κλειδί = the key

For many neuter nouns, the nominative and accusative forms are the same, which is why το κλειδί looks the same whether it is a subject or an object.

In this sentence, both can make sense depending on context.

Literally, κλειστό usually means closed. But with something like a locker, English often naturally says locked.

So in context:

• Το ντουλαπάκι ... είναι κλειστό can be understood as
  • The locker is closed
  • or more naturally, The locker is locked

Greek often leaves that slight ambiguity to context.

Greek word order is more flexible than English, because endings and articles help show grammatical roles. But the order here is very natural and straightforward:

• Το ντουλαπάκι = the subject
• στα αποδυτήρια = location
• είναι κλειστό = is locked/closed

So the sentence flows as: The locker in the changing rooms is locked, but I have the key.

Other word orders are possible for emphasis, for example:

• Στα αποδυτήρια το ντουλαπάκι είναι κλειστό...

But the original version is the most neutral and standard.

In practice, it tells you the location of the locker: the locker in the changing rooms.

So it is most naturally understood as modifying the noun phrase or locating the subject:

• the locker in the changing rooms

Greek often places location phrases after the noun like this very naturally.

You would make the noun and adjective plural:

• Τα ντουλαπάκια στα αποδυτήρια είναι κλειστά, αλλά έχω το κλειδί.

Changes:

• το ντουλαπάκι → τα ντουλαπάκια
• κλειστό → κλειστά

Everything else can stay the same if you still mean I have the key.

If you meant more than one key, then:

• έχω τα κλειδιά = I have the keys

It sounds like normal, everyday standard Greek.

Nothing in it is especially formal or literary:

• ντουλαπάκι is common spoken vocabulary
• στα αποδυτήρια is natural everyday phrasing
• είναι κλειστό
• αλλά έχω το κλειδί

All of this would sound perfectly normal in conversation.