Onlar geçen yıl evlendi.

• Onlar = they
• geçen = last / past (literally passing or that passed)
• yıl = year
• evlendi = got married

A very literal word-for-word gloss would be:

They last year got married.

Natural English is They got married last year.

Evlendi is in the simple past (often called the -di past in Turkish).

It is built like this:

• evlen- = the verb stem, from evlenmek (to get married)
• -di = past tense marker

So:

• evlenmek = to get married
• evlendi = he/she/it got married, or they got married depending on context

In this sentence, it means got married.

Because in Turkish, the 3rd person plural ending is often optional when the subject is already stated.

So both of these can be used:

• Onlar geçen yıl evlendi
• Onlar geçen yıl evlendiler

Both mean They got married last year.

Very generally:

• evlendi sounds natural and common
• evlendiler makes the plural a bit more explicit

Turkish often avoids repeating plural information if the subject already shows it.

Yes. Turkish often drops subject pronouns when they are understood from context.

So you could say:

• Geçen yıl evlendiler. = They got married last year.

That is very natural.

But with evlendi, there is a possible ambiguity, because evlendi can also mean:

• he got married
• she got married
• they got married (if context makes that clear)

So onlar is helpful when you want to clearly show they.

In this sentence, Turkish uses evlenmek, which means to get married.

That is a very important point:

• evlenmek = to get married
• not usually to marry someone directly

For example:

• Onlar evlendi. = They got married.
• Ali Ayşe'yle evlendi. = Ali got married to Ayşe.

English often says marry someone, but Turkish usually uses biriyle evlenmek = to get married with/to someone.

So this sentence is naturally understood as They got married last year, not They married last year in the English transitive sense.

Because Turkish time expressions often appear in a bare form when they mean when something happened.

Examples:

• bugün = today
• dün = yesterday
• geçen hafta = last week
• geçen yıl = last year

So geçen yıl simply functions as a time expression: last year.

You do not need a separate word like English in here.

Geçen comes from the verb geçmek (to pass).

In this phrase, geçen yıl literally means something like:

• the year that passed

But in normal English, the natural meaning is simply:

• last year

You will see this pattern a lot:

• geçen hafta = last week
• geçen ay = last month
• geçen gün = the other day / the past day, depending on context

No, Turkish word order is flexible, but the most neutral order usually keeps the verb near the end.

This sentence:

• Onlar geçen yıl evlendi

is a normal, natural order.

You may also hear:

• Geçen yıl onlar evlendi.

This still means They got married last year, but the emphasis may shift slightly.

The main thing to remember is that Turkish commonly puts the verb at the end in neutral sentences.

Yes. The -di past is the normal definite/simple past. It is typically used for a completed event presented as a fact.

So evlendi is a straightforward way to say:

• got married

Learners often compare it with -miş:

• evlendi = got married
• evlenmiş = apparently got married / I heard that they got married / it turns out they got married

So in your sentence, evlendi presents the event directly and plainly as a past fact.

Yes, it could, but only if the context already makes the subject clear.

By itself, Geçen yıl evlendi is more likely to be understood as:

• He/she got married last year

because evlendi is the same form for he/she/it and can sometimes also refer to they in context.

If you want to avoid ambiguity, use one of these:

• Onlar geçen yıl evlendi
• Geçen yıl evlendiler

Both make the plural meaning clearer.