Το καθήκον μου σήμερα είναι να τελειώσω την αναφορά πριν από τις έξι.

Because καθήκον is a neuter singular noun meaning duty, task, or obligation, so it takes the neuter singular definite article το.

• το καθήκον = the duty / the task
• το καθήκον μου = my duty

In Greek, possessive words like μου often come after the noun, not before it.

That is the normal Greek pattern with the weak possessive forms:

• μου = my
• σου = your
• του / της = his / her

So Greek usually says:

• το βιβλίο μου = my book
• η αναφορά μου = my report
• το καθήκον μου = my duty

Putting μου before the noun is not the normal pattern here. If you want extra emphasis, Greek often uses δικός / δική / δικό instead:

• δικό μου καθήκον = a duty of my own / my own duty

It is in the nominative, because it is the subject of the sentence.

The full subject is:

• Το καθήκον μου σήμερα = my duty today

Then the predicate is:

• είναι να τελειώσω την αναφορά πριν από τις έξι = is to finish the report before six

One small complication: with many neuter nouns, the nominative and accusative look the same, so the form καθήκον does not visibly change.

Σήμερα means today. It is an adverb, so it tells you when the duty applies.

In this sentence:

• Το καθήκον μου σήμερα = my duty today

Greek word order is flexible, so you could also say:

• Σήμερα το καθήκον μου είναι να τελειώσω την αναφορά πριν από τις έξι.

That means the same thing, but the emphasis shifts a little. Putting σήμερα first highlights today more strongly.

The structure είναι να + verb means something like:

• is to ...
• is supposed to ...
• has to ...
  depending on context.

So:

• Το καθήκον μου σήμερα είναι να τελειώσω...
  means My duty today is to finish...

This is a very normal Greek way to express purpose, obligation, or what is expected.

Modern Greek usually does not use an infinitive the way English does. Where English says:

• to finish

Greek normally uses:

• να τελειώσω

Here να introduces the subjunctive-type verb form. So after είναι in this pattern, you need να:

• είναι να τελειώσω = is to finish

Without να, the sentence would be ungrammatical.

Τελειώσω is the aorist subjunctive form after να.

That sounds technical, but the key idea is simple: it presents the action as one whole completed action.

So:

• να τελειώσω την αναφορά = to finish the report

This fits well because finishing a report is seen as a single completed result.

If you used να τελειώνω, that would suggest a more ongoing, repeated, or less bounded action, which is not the natural choice here.

Because αναφορά is the direct object of τελειώσω.

You are finishing the report, so the noun must be in the accusative:

• η αναφορά = the report as subject
• την αναφορά = the report as object

So:

• τελειώσω την αναφορά = finish the report

This is a very common pattern in Greek: the article changes with the case.

Here αναφορά means report.

Depending on context, αναφορά can also mean things like reference or mention, but in this sentence the meaning is clearly report because it is something that can be finished.

So:

• την αναφορά = the report

Πριν από means before.

So:

• πριν από τις έξι = before six

It is a very common way to express that something happens earlier than a certain time.

You may also hear πριν τις έξι in everyday speech, but πριν από τις έξι is very clear and standard.

Greek often uses the article with clock times.

So you get patterns like:

• στις έξι = at six
• πριν από τις έξι = before six
• μετά τις έξι = after six

The article is feminine plural because Greek is really understood as referring to hours:

• τις έξι (ώρες)

Even though ώρες is not spoken, it is felt in the grammar.

Not exactly.

• πριν από τις έξι = before six, earlier than six
• by six in English often means at or before six

If you want the Greek idea of by six in the sense of no later than six, Greek often uses:

• μέχρι τις έξι
• ως τις έξι

So the Greek sentence is slightly stricter than English by six if you take it literally: it says before six, not at or before six.

No. Greek word order is fairly flexible.

The original sentence is perfectly natural:

• Το καθήκον μου σήμερα είναι να τελειώσω την αναφορά πριν από τις έξι.

But you could also say:

• Σήμερα το καθήκον μου είναι να τελειώσω την αναφορά πριν από τις έξι.

Both are correct. The difference is mostly emphasis:

• starting with Σήμερα emphasizes today
• starting with Το καθήκον μου emphasizes my duty

Yes, a little. Καθήκον often sounds more like duty, responsibility, or obligation than a casual task.

So this sentence sounds natural, but somewhat serious or formal.

In more everyday speech, depending on the context, someone might also say:

• Η δουλειά μου σήμερα είναι να... = My job/task today is to...
• Ο στόχος μου σήμερα είναι να... = My goal today is to...

But καθήκον is absolutely correct and natural if you want the sense of duty.

Yes. Ολοκληρώσω is also very natural here.

Compare:

• να τελειώσω την αναφορά = to finish the report
• να ολοκληρώσω την αναφορά = to complete the report

Ολοκληρώσω can sound a little more formal or polished, while τελειώσω is more everyday and straightforward. Both work well in this kind of sentence.