Το καινούριο πολύπριζο είναι πιο ασφαλές από το παλιό, αλλά θέλει προσοχή όταν το βάζω στην πρίζα.

Because πολύπριζο is a neuter singular noun. In the sentence, it is the subject of είναι, so it is in the nominative case.

That means:

• το = the neuter singular article
• καινούριο = neuter singular form of καινούριος / καινούργιος
• πολύπριζο = neuter singular noun

All three agree with each other:

• το καινούριο πολύπριζο

Greek adjectives usually have to match the noun in gender, number, and case.

Πολύπριζο means a power strip, multi-socket adapter, or extension block with several outlets.

It is built from:

• πολύ- = many
• πρίζα = socket / outlet

So it is literally something like many-socket.

Yes. Καινούριο and καινούργιο are both common forms meaning new.

So these are both natural:

• το καινούριο πολύπριζο
• το καινούργιο πολύπριζο

In everyday Greek, both are used. A learner will hear both.

Because ασφαλές is the neuter singular form of the adjective ασφαλής (safe).

This adjective has forms like:

• masculine/feminine: ασφαλής
• neuter: ασφαλές

Since πολύπριζο is neuter singular, the adjective must match it:

• Το πολύπριζο είναι ασφαλές.

This is very common with adjectives ending in -ής / -ές.

This is the normal Greek way to make a comparison:

• πιο = more
• ασφαλές = safe
• από = than

So:

• πιο ασφαλές από το παλιό = safer than the old one

This pattern is extremely common:

• πιο μεγάλο από... = bigger than...
• πιο ακριβό από... = more expensive than...
• πιο εύκολο από... = easier than...

Because Greek, like English, often leaves out a noun when it is obvious from context.

So:

• το παλιό literally means the old one
• the full version would be το παλιό πολύπριζο

Greek does this very naturally with articles and adjectives:

• το καινούριο = the new one
• το παλιό = the old one
• η μεγάλη = the big one
• τα μικρά = the small ones

Literally, θέλει προσοχή means it wants attention/care.

But idiomatically, it means:

• it needs care
• it requires caution
• you have to be careful with it

Greek often uses θέλει in this kind of impersonal, idiomatic way:

• Θέλει χρόνο. = It takes time.
• Θέλει δουλειά. = It needs work.
• Θέλει προσοχή. = It needs caution / You need to be careful.

So in this sentence, it does not mean the power strip literally wants something in the human sense.

Because προσοχή here is being used in a general, uncountable sense: care / caution / attention.

Greek often leaves out the article with abstract nouns in this kind of expression:

• θέλει προσοχή = it needs caution
• θέλει υπομονή = it needs patience
• θέλει χρόνο = it needs time

If you added an article, it would usually sound more specific or would change the nuance.

Because όταν means when, and it introduces a time clause.

So:

• όταν το βάζω στην πρίζα = when I plug it into the socket

You use να for a different kind of structure, usually after verbs that express wanting, being able, needing, etc. For example:

• Θέλω να το βάλω στην πρίζα. = I want to plug it in.

But after όταν, you normally just use a verb form directly:

• όταν έρχεται = when he comes
• όταν φεύγω = when I leave
• όταν το βάζω = when I plug it in

Το is the direct object pronoun meaning it, and it refers to το καινούριο πολύπριζο.

So:

• βάζω το πολύπριζο στην πρίζα = I plug the power strip into the outlet
• το βάζω στην πρίζα = I plug it into the outlet

Because πολύπριζο is neuter singular, the pronoun is also το.

Yes. Βάζω means I put / I plug in, so the sentence is specifically from the speaker’s point of view:

• when I plug it into the outlet

Greek often uses the present tense here for something habitual or generally true:

• όταν το βάζω στην πρίζα = when I plug it in / whenever I plug it in

If the sentence wanted to say when you plug it in, it would be:

• όταν το βάζεις στην πρίζα

If it wanted to sound more general or impersonal, Greek could also phrase it differently.

Στην is a contraction of:

• σε + την = στην

So:

• στην πρίζα = into/in the socket

After σε, Greek uses the accusative case:

• την πρίζα

This is a very common contraction:

• σε το → στο
• σε τη / την → στη / στην
• σε τον → στον

So βάζω κάτι στην πρίζα means I plug something into the socket/outlet.

They are two different things:

• πολύπριζο = the power strip / multi-outlet device
• πρίζα = the wall socket / outlet

So the sentence is talking about putting the power strip into the wall outlet.

That is why both words appear:

• Το καινούριο πολύπριζο = the new power strip
• το βάζω στην πρίζα = I plug it into the wall socket

Yes, Greek word order is fairly flexible, but this order is the most neutral and natural here.

The sentence starts with the topic/subject:

• Το καινούριο πολύπριζο

Then gives the main statement:

• είναι πιο ασφαλές από το παλιό

Then adds a contrast:

• αλλά θέλει προσοχή...

Greek could move things around for emphasis, but the given order is straightforward and normal for everyday speech and writing.

Yes. Αλλά is the standard Greek word for but.

Here it connects two contrasting ideas:

• the new power strip is safer than the old one
• but it still requires caution

So the logic is: safer does not mean completely risk-free.

Yes, it often carries a mild warning tone. Depending on context, it can mean:

• be careful
• handle it carefully
• it needs caution
• you should pay attention

In this sentence, it suggests: even though the new power strip is safer, plugging it in is still something you should do carefully.

So it sounds practical and natural, not dramatic, but definitely cautionary.