Έστω κι αν διαφωνεί, συζητάμε το θέμα.

It is a concessive expression meaning even if, even though, or granted that.

So Έστω κι αν διαφωνεί, συζητάμε το θέμα means something like:

• Even if he/she disagrees, we discuss the issue
• Even though he/she disagrees, we discuss the matter

The basic idea is: the disagreement does not stop the discussion.

Also, έστω κι αν is best learned as a fixed phrase. Its literal parts do not help very much in translation.

κι is a shortened form of και. It is extremely common in modern Greek, especially before a vowel, and it sounds natural here.

So these are equivalent:

• έστω κι αν
• έστω και αν

In this sentence, κι is just the more natural, compact form.

διαφωνεί means he/she disagrees or he/she is disagreeing, depending on context.

It is the 3rd person singular form of διαφωνώ = to disagree.

So διαφωνεί can refer to:

• he disagrees
• she disagrees
• sometimes it disagrees, though that is less likely here

Greek often leaves out the subject pronoun, so you do not see a separate word for he or she.

Because Greek is a pro-drop language. That means the subject pronoun is often omitted when the verb ending already shows the person and number.

Here, διαφωνεί already tells you it is 3rd person singular, so Greek does not need to say:

• αυτός διαφωνεί = he disagrees
• αυτή διαφωνεί = she disagrees

Unless the speaker wants emphasis or contrast, the pronoun is usually left out.

συζητάμε means we discuss or we are discussing.

It is the 1st person plural form of συζητάω / συζητώ = to discuss.

So:

• συζητάμε = we discuss / we are discussing

This is a very common everyday form. You may also see συζητούμε, which is more formal or stylistically different, but συζητάμε is completely standard.

It can mean either one.

The Greek present tense often covers both:

• a simple present idea: we discuss
• a progressive idea: we are discussing

Context tells you which is more natural in English.

So this sentence could mean:

• Even if he/she disagrees, we discuss the issue
  or
• Even if he/she disagrees, we are discussing the issue

English forces you to choose more often than Greek does.

Because αν and να do different jobs.

• να introduces many subordinate clauses, often with a subjunctive-type meaning
• αν means if and introduces conditional or concessive clauses by itself

So after αν, you normally do not add να.

That is why you get:

• αν διαφωνεί = if he/she disagrees

not:

• αν να διαφωνεί ❌

In έστω κι αν διαφωνεί, the αν already sets up the even if idea.

Because the first part, Έστω κι αν διαφωνεί, is an introductory subordinate clause.

Greek commonly separates this kind of opening clause from the main clause with a comma:

• Έστω κι αν διαφωνεί, συζητάμε το θέμα.

This is very similar to English punctuation in sentences like:

• Even if he disagrees, we discuss the issue.

το θέμα is the direct object of συζητάμε.

• συζητάμε = we discuss
• το θέμα = the issue / the topic / the matter

So the structure is:

• we discuss
  • the issue

A small extra point: θέμα is a neuter noun, and in the singular its nominative and accusative forms look the same, so the form itself does not change here.

Yes. Greek word order is fairly flexible.

For example, you could also say:

• Συζητάμε το θέμα, έστω κι αν διαφωνεί.

This puts the main action first and the concessive idea after it.

The original sentence:

• Έστω κι αν διαφωνεί, συζητάμε το θέμα.

puts more emphasis on the contrast: despite the disagreement, the discussion still happens.

They are similar, but not always identical.

• έστω κι αν = even if / even though, somewhat formal or literary in some contexts
• ακόμα κι αν = even if, very common
• παρόλο που = although / even though

So you could often replace it with:

• Ακόμα κι αν διαφωνεί, συζητάμε το θέμα.

That sounds very natural too.

But παρόλο που is a little more like although / even though and may sound more factual than hypothetical, depending on context.

It could be either, depending on context.

Because both verbs are in the present tense, the sentence may mean:

• a general principle: Even if he/she disagrees, we discuss the issue
• a current situation: Even though he/she disagrees, we are discussing the issue

Greek leaves that a bit open, and the surrounding context would make it clear.

It sounds neutral to slightly formal, mainly because of έστω κι αν.

The sentence gives the sense of a principle or policy:

• disagreement exists,
• but discussion continues anyway.

So it can sound like:

• We discuss the matter regardless of disagreement
• Disagreement is not a reason to avoid discussion

That is one reason this wording can feel a little more thoughtful or formal than very everyday speech.