Doksan öğrenci odaya girdi.

After a number, Turkish normally uses the noun in the singular form.

So:

doksan öğrenci = ninety students

Even though English uses a plural noun after numbers, Turkish usually does not. Using öğrenciler after doksan would sound non-neutral in ordinary Turkish.

Oda means room.

The ending -(y)a / -(y)e is the dative case, often meaning to, into, toward.

So:

oda → odaya = to the room / into the room

The y appears because oda ends in a vowel. Turkish often inserts a buffer consonant between two vowels:

oda + a → odaya

This is because the verb girmek normally takes its destination in the dative.

So Turkish says:

odaya girmek = literally something like to go in to the room

This is simply the normal pattern of the verb.

Compare:

odaya = into the room / to the room
odada = in the room
odadan = from the room

Girdi breaks down as:

gir- = enter, go in
-di = simple past tense

So girdi means entered or went in.

In this sentence, it is the past-tense verb for the whole subject doksan öğrenci.

The Turkish past-tense suffix changes according to vowel harmony and consonant voicing.

The suffix is often shown as -DI, where:

• D can become d or t
• I can become ı, i, u, or ü

In gir-, the last vowel is i, so the suffix vowel becomes i.

Also, the stem ends in r, which is voiced, so the suffix uses d, not t.

So:

gir- + -di → girdi

With a subject that includes a number, Turkish normally uses the singular verb form.

So:

Doksan öğrenci odaya girdi is the standard, natural form.

This fits a broader Turkish pattern: when the number already makes plurality clear, Turkish often avoids adding extra plural marking.

No. Turkish word order is fairly flexible, although the verb usually comes at the end in a neutral statement.

Doksan öğrenci odaya girdi is a natural, neutral order.

You could also say:

Odaya doksan öğrenci girdi

That still means the same thing, but it gives a bit more emphasis to odaya.

So the order can shift for emphasis, topic, or style.

Turkish does not have articles exactly like English a/an and the.

Meaning is often understood from context, case endings, and sentence structure.

Here, odaya is naturally understood as into the room in context.

If you specifically wanted into a room, you could say:

bir odaya

where bir can mean a / one.

It can correspond to either in English, depending on context.

The verb girmek basically means to enter / to go in. So:

odaya girdi can be translated as:

• entered the room
• went into the room

English chooses the most natural wording, but the Turkish form is the same.

Yes. Doksan öğrenci is the subject, and it means ninety students.

The rest of the sentence tells you where they went and what happened:

• odaya = into the room
• girdi = entered / went in

So the basic structure is:

[subject] + [destination] + [verb]

which is very common in Turkish.