Δεν ξέρω το νόημα αυτής της φράσης.

Δεν is the standard negation word used before verbs in Modern Greek. It means not.

So:

• ξέρω = I know
• δεν ξέρω = I do not know / I don't know

In normal statements, δεν goes directly before the verb.

Ξέρω means I know in the sense of I am aware of, I understand, or I know a fact/information.

It is the 1st person singular form of ξέρω:

• ξέρω = I know
• ξέρεις = you know
• ξέρει = he/she/it knows

It is used here because the speaker is saying they do not know or understand the meaning of something.

A learner might compare it with γνωρίζω, which also relates to knowing, but γνωρίζω is more often used for knowing/being acquainted with a person, place, or subject, or meeting/getting to know. In this sentence, ξέρω is the natural choice.

Greek often uses the definite article where English might or might not use the.

• το = the (neuter singular)
• νόημα = meaning

So το νόημα literally means the meaning.

In this sentence, Greek normally wants the article because you are talking about the specific meaning of a specific phrase. Leaving out the article here would sound unnatural.

Νόημα is in the accusative singular because it is the direct object of the verb ξέρω.

The structure is:

• Δεν ξέρω = I don't know
• what don't I know? → το νόημα

So το νόημα is the thing that is not known.

In neuter nouns like νόημα, the nominative and accusative are often identical, so the form does not change.

This is a very common Greek structure.

• αυτής = of this
• της = of the
• φράσης = phrase

Together, αυτής της φράσης means of this phrase.

Greek demonstratives like αυτός, αυτή, αυτό usually appear together with the article:

• αυτή η φράση = this phrase
• αυτής της φράσης = of this phrase

So the article does not disappear when you use this. Greek normally says both.

Because it is in the genitive singular.

The basic form is:

• η φράση = the phrase

But here the meaning is the meaning of this phrase, so Greek uses the genitive:

• της φράσης = of the phrase

That is why φράση changes to φράσης.

This is a very important pattern in Greek:

• η λέξη → της λέξης
• η πρόταση → της πρότασης
• η φράση → της φράσης

Because it depends on το νόημα.

Greek often expresses X of Y by putting Y in the genitive.

So:

• το νόημα = the meaning
• της φράσης = of the phrase

Together:

• το νόημα της φράσης = the meaning of the phrase

Since the speaker means of this phrase, the full form becomes:

• το νόημα αυτής της φράσης

So the genitive answers the question meaning of what?

Yes, Greek word order is more flexible than English, because case endings show the grammatical role of words.

The sentence as given:

• Δεν ξέρω το νόημα αυτής της φράσης.

is the most neutral and natural way to say it.

But you may also hear:

• Δεν ξέρω το νόημα της φράσης αυτής.

This also means I don't know the meaning of this phrase, but it sounds a little more formal or stylistically different.

In everyday Greek, the original version with αυτής της φράσης before or together as a unit is very common.

Yes, ξέρω is present tense: I know.

Greek uses the present tense here for a present state, just like English does:

• I know
• I don't know

So Δεν ξέρω literally and naturally means I don't know.

It is not a continuous action here; it describes your current state of knowledge.

A rough pronunciation is:

Dhen KSÉ-ro to NÓ-i-ma af-TÍS tis FRÁ-sis

A few useful notes:

• Δεν sounds like dhen; the δ is like the th in this
• ξ = ks
• νόημα has three syllables: NÓ-i-ma
• αυτής is pronounced af-TIS here, because αυ is pronounced av/af depending on the next sound
• φράσης begins with f

The main written stress falls on:

• ξέρω
• νόημα
• αυτής
• φράσης

Yes, and it means something slightly different in nuance.

• Δεν ξέρω το νόημα... = I don't know the meaning...
• Δεν καταλαβαίνω το νόημα... = I don't understand the meaning...

The first focuses on not knowing. The second focuses on not understanding.

In many situations they are close, but they are not always identical. The original sentence is specifically about knowing the meaning.

Yes, it is completely natural and correct.

A Greek speaker might also say similar things such as:

• Δεν ξέρω τι σημαίνει αυτή η φράση. = I don't know what this phrase means.
• Δεν καταλαβαίνω αυτή τη φράση. = I don't understand this phrase.

But Δεν ξέρω το νόημα αυτής της φράσης is a perfectly normal sentence, especially when you want to talk specifically about the meaning.