Η καθηγήτρια ρώτησε ποιο επίθετο ταιριάζει καλύτερα σε αυτή τη φράση.

It is an indirect question embedded inside the main sentence.

• Main clause: Η καθηγήτρια ρώτησε = The teacher asked
• Embedded question: ποιο επίθετο ταιριάζει καλύτερα σε αυτή τη φράση = which adjective fits this phrase best

That is why Greek does not use ότι or πως here. Those would introduce a statement, not a question.

Ποιο is the neuter singular form of the interrogative word meaning which or what.

It agrees with επίθετο, which is a neuter singular noun:

• ποιος = masculine
• ποια = feminine
• ποιο = neuter

So Greek says ποιο επίθετο because επίθετο is neuter.

It can be understood as either, depending on how natural the English translation is.

In this sentence, which adjective is usually the most natural English version, because the speaker is choosing among possible adjectives. But Greek ποιο can sometimes correspond to English what in similar contexts.

Here, επίθετο means adjective.

Be careful: επίθετο can also mean surname / last name in other contexts. Greek often uses the same word for both meanings, so you have to rely on context. In this sentence, because of ταιριάζει καλύτερα σε αυτή τη φράση, it clearly means the grammar word adjective.

Because its subject is ποιο επίθετο, which is singular.

So Greek is literally saying:

• which adjective fits best

The verb ταιριάζει is the 3rd person singular present form of ταιριάζω, meaning fit, match, or suit.

Because καλύτερα is an adverb, and it modifies the verb ταιριάζει.

The idea is fits better / best, not a better adjective. English uses better for both adjective and adverb, but Greek usually distinguishes them more clearly.

So:

• καλύτερο = better (adjective form)
• καλύτερα = better / best (adverb form, depending on context)

Here it means fits better or idiomatically fits best.

Because Greek commonly uses demonstrative + article + noun.

So:

• αυτή = this
• τη φράση = the phrase

Together, αυτή τη φράση means this phrase.

This is normal Greek structure. English says this phrase, but Greek often keeps the article as well.

After σε, Greek normally uses the accusative.

So φράση appears in the feminine singular accusative:

• nominative: η φράση
• accusative: τη(ν) φράση

That is why you get σε αυτή τη φράση = in / to / for this phrase, depending on context. Here σε is best understood as for or with respect to this phrase.

Both are possible, but τη is a very common shortened form of την before a consonant.

So:

• την φράση = full form
• τη φράση = very common reduced form

In everyday Greek, the shorter form is extremely normal.

Greek uses the definite article much more often than English.

So Η καθηγήτρια is the normal way to say the teacher / the female professor as the subject of the sentence. The article η also tells you the noun is:

• feminine
• singular
• nominative

English might sometimes just say Teacher asked... in special contexts, but Greek normally keeps the article in an ordinary sentence like this.

Ρώτησε is the aorist form, which here corresponds to a simple past: asked.

More specifically, it is 3rd person singular aorist active of ρωτάω / ρωτώ. So:

• ρωτάει = asks / is asking
• ρώτησε = asked

In this sentence, it simply reports a completed past action: the teacher asked.

No, Greek word order is fairly flexible, but this version is the most neutral and natural.

The sentence follows a very clear pattern:

• Η καθηγήτρια = subject
• ρώτησε = verb
• ποιο επίθετο... = embedded question

You could move things around for emphasis, but the given order is the standard one a learner should be comfortable with first.