Learn Hardcore Greek: Στο πανεπιστήμιο η αδερφή μου σπουδάζει ιστορία. - At the university my sister studies history.

The preposition σε (“at / in / to”) always takes the accusative in Modern Greek.
Neuter singular nouns in -ο have the same form in nominative and accusative:
- Nominative: το πανεπιστήμιο
- Accusative: το πανεπιστήμιο

So στο πανεπιστήμιο is σε + το + accusative, but the form of the noun doesn’t change between nominative and accusative.

Why does the sentence start with Στο πανεπιστήμιο instead of with “my sister”?

Greek word order is relatively flexible. Starting with Στο πανεπιστήμιο puts emphasis on the place:

Στο πανεπιστήμιο η αδερφή μου σπουδάζει ιστορία.
Literally: At the university, my sister studies history.

You can also say:

Η αδερφή μου σπουδάζει ιστορία στο πανεπιστήμιο.

Both are correct. The second is closer to neutral English word order; the original version foregrounds the location.

Why do we say η αδερφή μου with a definite article when English just says “my sister”?

In Greek, when you use a possessive pronoun like μου (“my”), you normally also use the definite article:

η αδερφή μου = my sister (literally: the sister my)
ο αδερφός μου = my brother
το σπίτι μου = my house

Leaving out the article (αδερφή μου) sounds incomplete or unusual in standard Modern Greek, except in a few special fixed expressions.

Why is μου placed after the noun instead of before it, like “my sister”?

The word μου is a clitic (weak) possessive pronoun. In Greek, these weak possessives usually:

Follow the noun
Don’t get their own stress

So:

η αδερφή μου = my sister
ο πατέρας μου = my father
η φίλη μου = my (female) friend

There is also a strong form that can stand before a noun (η δική μου αδερφή = my own sister), but that adds emphasis and is less neutral.

What person and tense is σπουδάζει, and what is the base verb?

The base verb is σπουδάζω = to study (as in university studies).

σπουδάζει is:

3rd person singular (he / she / it)
Present tense

So it means “he studies / she studies / it studies” or “he / she is studying”, depending on context.

Does σπουδάζει mean “studies” or “is studying”? How do you say the continuous form?

Modern Greek present tense covers both simple and continuous meanings:

Η αδερφή μου σπουδάζει ιστορία.
- can mean “My sister studies history.”
- or “My sister is studying history.”

You don’t need a separate auxiliary like “is” to make a continuous form. Context tells you which English translation fits better.

Why is there no article before ιστορία? Shouldn’t it be την ιστορία?

When talking about fields of study, school subjects, or languages in general, Greek often omits the article:

σπουδάζει ιστορία = she studies history (as a subject in general)
μαθαίνει γαλλικά = he learns French

If you say την ιστορία, it usually means a specific history:

σπουδάζει την ιστορία της Ελλάδας.
= She studies the history of Greece (a specific history)

What gender is ιστορία, and what case is it in this sentence?

Ιστορία is a feminine noun.

In this sentence, it is the direct object of the verb σπουδάζει, so it is in the accusative case:

Nominative: η ιστορία
Accusative: την ιστορία (article changes, noun form stays the same)

Because the article is omitted here, you only see ιστορία, which has the same form in nominative and accusative in Modern Greek.

Is there a difference between αδερφή and αδελφή?

They are essentially the same word, meaning “sister”.

αδερφή reflects the modern pronunciation.
αδελφή is closer to the older spelling and is often seen as slightly more formal or conservative.

In everyday Modern Greek, αδερφή is very common, but both forms are understood and used.

Can I change the word order to Η αδερφή μου στο πανεπιστήμιο σπουδάζει ιστορία?

Yes, that is grammatically possible:

Η αδερφή μου στο πανεπιστήμιο σπουδάζει ιστορία.

This tends to sound like you are slightly emphasizing “at university” as extra information about “my sister”. The differences are mainly about information structure and emphasis, not about grammatical correctness. All of the following are fine:

Στο πανεπιστήμιο η αδερφή μου σπουδάζει ιστορία.
Η αδερφή μου σπουδάζει ιστορία στο πανεπιστήμιο.
Η αδερφή μου στο πανεπιστήμιο σπουδάζει ιστορία.

Could you give a rough pronunciation (in Latin letters) of the whole sentence?

A simple phonetic approximation:

Στο → sto
πανεπιστήμιο → pan-eh-PEE-stee-mio (stress on -PEE-)
η → i (like “ee”)
αδερφή → a-ther-FEE (stress on -FEE)
μου → mu (like “moo” but shorter)
σπουδάζει → spu-THA-zee (stress on -THA-, with soft th as in “this”)
ιστορία → ee-sto-REE-a (stress on -REE-)

So together:
Sto pan-eh-PEE-stee-mio i a-ther-FEE mu spu-THA-zee ee-sto-REE-a.

Why doesn’t μου change according to the gender of αδερφή?

The weak possessive μου is invariable; it does not change with:

gender (masculine / feminine / neuter)
number (singular / plural)

So:

ο αδερφός μου = my brother
η αδερφή μου = my sister
το παιδί μου = my child
οι φίλοι μου = my friends

The noun and its article change for gender and number, but μου stays the same.