Ο εμβολιασμός έγινε χτες.

Ο is the definite article meaning the.

It appears as ο because εμβολιασμός is a masculine singular noun in the nominative case.

So:

• ο εμβολιασμός = the vaccination

Greek articles change according to gender, number, and case, unlike English the, which always stays the same.

εμβολιασμός means vaccination.

A learner may confuse it with εμβόλιο, but they are different:

• εμβολιασμός = vaccination (the process/event)
• εμβόλιο = vaccine (the shot/substance)

So this sentence is talking about the vaccination event, not the vaccine itself.

έγινε is the aorist form of γίνομαι, which often means:

• to happen
• to become
• to take place
• in some contexts, to be done

In this sentence, έγινε means something like:

• happened
• took place
• was done

So Ο εμβολιασμός έγινε χτες is literally close to:

• The vaccination happened yesterday
• The vaccination took place yesterday

Even if the natural English translation might be The vaccination was done yesterday, the Greek verb is built from γίνομαι, not from the ordinary verb to be.

Because Greek often expresses this idea with γίνομαι rather than with a direct equivalent of English was.

Compare the idea:

• English: The vaccination was done yesterday
• Greek: The vaccination happened/took place yesterday

This is a very normal Greek way to describe an event. It sounds natural because the sentence focuses on the fact that the vaccination occurred.

Not exactly.

It may feel passive in English because we might translate it as was done, but grammatically έγινε is the 3rd person singular aorist of γίνομαι.

So the structure is not a regular passive of εμβολιάζω. Instead, it is more like:

• the vaccination happened
• the vaccination took place

That is why it is better to understand έγινε here as an event verb, not simply as a passive form.

It is the aorist, which is one of the main Greek past tenses.

Here the aorist presents the action/event as a completed whole:

• έγινε = it happened / it took place

This fits well with χτες because the sentence refers to a single completed event in the past.

χτες means yesterday.

It is very common in everyday Greek. You may also see:

• χθες

Both mean yesterday. In many contexts, χτες feels a bit more everyday or conversational, while χθες may look a little more formal or standard in writing. But both are widely understood and used.

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

This sentence is:

• Ο εμβολιασμός έγινε χτες.

But you could also hear:

• Χτες έγινε ο εμβολιασμός.
• Έγινε χτες ο εμβολιασμός.

These all mean basically the same thing, though the emphasis can shift:

• starting with χτες emphasizes yesterday
• starting with ο εμβολιασμός makes the vaccination the topic

The original sentence is a neutral, natural way to say it.

Because εμβολιασμός is the subject of the sentence, so it stays in the nominative case:

• ο εμβολιασμός

Greek nouns change form depending on their role in the sentence, but here the noun is doing the role of the subject: the vaccination happened.

So nominative is exactly what you would expect.

A simple pronunciation guide is:

• Ο εμβολιασμός έγινε χτες
• roughly: o em-vo-liaz-MOS E-yee-neh htes

A few useful notes:

• σμ in εμβολιασμός is pronounced smoothly together
• γ before ι in έγινε sounds like a soft y-like sound
• χ in χτες is not like English h; it is a rougher throat sound, similar to the ch sound in some pronunciations of German Bach

You do not need perfect pronunciation right away, but it helps to notice that Greek sounds are often more consistent than English spelling suggests.

Normally, no, not in standard Greek for this sentence.

Greek uses the definite article much more often than English does. Since we are talking about a specific event, ο εμβολιασμός sounds natural.

Without the article, Εμβολιασμός έγινε χτες would sound unnatural in ordinary standard usage.

It is mostly neutral, with one slightly conversational element:

• χτες is a common everyday form of yesterday

If you wanted a slightly more formal version, you might write:

• Ο εμβολιασμός έγινε χθες.

But the original sentence is completely normal and natural.