Το περιστατικό συνέβη χτες.

Yes. συνέβη is the simple past form of the verb συμβαίνω (to happen).

So:

• συμβαίνω = I happen / it happens
• συνέβη = it happened

In this sentence, the subject is το περιστατικό (the incident), so συνέβη means happened:
Το περιστατικό συνέβη χτες = The incident happened yesterday.

Because συμβαίνω is an irregular verb in the past tense. Its simple past is συνέβη, not a fully predictable form.

This is one of those verb forms you should learn as a whole:

• συμβαίνω = I happen / occur
• συνέβη = happened

Greek has many verbs whose past forms are not built in the most regular way, so this is a good one to memorize.

Περιστατικό means incident, event, or sometimes case, depending on context.

It takes το because it is a neuter singular noun:

• το περιστατικό = the incident

So:

• το = the for a neuter singular noun
• περιστατικό = incident

The ending -ό is a common sign of a neuter noun, though not every noun follows a simple pattern.

Yes. Το περιστατικό is the subject of the sentence, so it is in the nominative case.

The sentence structure is basically:

• Το περιστατικό = subject
• συνέβη = verb
• χτες = time expression

Since the incident is the thing that happened, it is the subject.

Χτες means yesterday.

It is very common in everyday Greek. You will also see χθες, which means the same thing.

• χτες = common everyday spelling/pronunciation
• χθες = more conservative/traditional spelling

Both are correct, and both mean yesterday.

Because Greek usually does not need a dummy subject like English it.

In English, you often need a subject even when it does not refer to anything specific:

• It happened yesterday.

In Greek, you can simply say:

• Συνέβη χτες. = It happened yesterday.

And if you want to specify what happened, you can add the noun:

• Το περιστατικό συνέβη χτες.

So Greek does not use a meaningless subject word the way English often does.

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

The neutral version here is:

• Το περιστατικό συνέβη χτες.

But you might also hear:

• Χτες συνέβη το περιστατικό.
• Συνέβη χτες το περιστατικό.

These alternatives can shift the emphasis slightly:

• starting with χτες emphasizes the time
• starting with συνέβη can sound more narrative or dramatic

Still, Το περιστατικό συνέβη χτες is a very natural standard sentence.

Because χτες works directly as an adverb of time, like yesterday in English.

So Greek says simply:

• χτες = yesterday

No preposition is needed.

Compare:

• σήμερα = today
• αύριο = tomorrow
• χτες = yesterday

All of these can appear by themselves without a preposition.

A simple pronunciation guide is:

• Το = to
• περιστατικό = pe-ri-sta-ti-KO
• συνέβη = si-NE-vi
• χτες = htes or roughly ktes with a breathy/ch-like start, depending on accent and speaker

The stressed syllables are:

• περιστατικό
• συνέβη

The accent marks show you where the stress goes.

Greek accent marks show which syllable is stressed.

In συνέβη, the stress falls on the last syllable:

• συ-νέ-βη

Accent marks are very important in Greek because stress is part of the normal written form of the word. They are not optional in standard writing.

Yes, in some contexts you could, but it is not exactly the same.

• συνέβη = happened / occurred
• έγινε = happened / took place / became / was done, depending on context

For an incident or event, both may be possible, but συνέβη often sounds especially natural for an event occurring.

So:

• Το περιστατικό συνέβη χτες. = The incident happened yesterday.
• Το περιστατικό έγινε χτες. = The incident happened/took place yesterday.

The first is often a bit more precise for occurred.

Yes, absolutely, if the context already makes it clear what you are talking about.

• Συνέβη χτες. = It happened yesterday.

Greek often omits things that are understood from context. If the listener already knows which event or incident you mean, the full noun phrase is not necessary.

It works in both, but it feels very natural in everyday Greek, especially because of χτες.

A slightly more formal or written-looking version might be:

• Το περιστατικό συνέβη χθες.

So the difference is mostly in χτες / χθες, not in the rest of the sentence.