Η εξέταση της ένστασης τελειώνει σήμερα.

Because they belong to different nouns and different cases.

• Η εξέταση = the examination / the review
  
  • Η is the feminine singular nominative article.
• της ένστασης = of the objection / of the appeal
  
  • της is the feminine singular genitive article.

So the sentence has:

• Η εξέταση = the examination
• της ένστασης = of the objection

In English, of the is often shown with a separate word, but in Greek the noun changes case, and the article changes too.

Because it is in the genitive singular, not the nominative.

The basic dictionary form is:

• η ένσταση = the objection / the appeal

But after a noun like εξέταση when you want to say examination of the objection, Greek uses the genitive:

• της ένστασης = of the objection

So:

• η ένσταση = nominative
• της ένστασης = genitive

This is very common in Greek. English often uses of, while Greek often uses the genitive case.

It is a noun phrase meaning:

• the examination/review of the objection

Breakdown:

• Η εξέταση = the examination / review
• της ένστασης = of the objection

So the structure is:

• article + noun + genitive phrase

This is one of the most common Greek patterns for showing possession or association:

• το τέλος της ημέρας = the end of the day
• η απόφαση του δικαστηρίου = the decision of the court
• η εξέταση της ένστασης = the examination of the objection

Τελειώνει is the 3rd person singular present tense of τελειώνω.

Here it agrees with η εξέταση, which is singular:

• η εξέταση τελειώνει = the examination ends / is ending

So the verb form means:

• he/she/it ends
• or in this context, it ends

Because η εξέταση is the subject, English uses it.

Because Greek, like English, often uses the present tense for things happening now or for scheduled/current events.

So:

• τελειώνει σήμερα can mean ends today
• depending on context, it can also feel like is ending today

This is normal and natural Greek. It does not have to mean a repeated action.

It can mean either, depending on context.

With something like η εξέταση as the subject, English usually prefers:

• ends
• or is completed / finishes

So:

• Η εξέταση της ένστασης τελειώνει σήμερα. = The review of the objection ends today.

A helpful point: τελειώνω can be used both:

1. intransitively:
   
   • Η ταινία τελειώνει. = The film ends.
2. transitively:
   
   • Τελειώνω τη δουλειά. = I finish the work.

Here it is intransitive: the examination ends.

Yes, it could go somewhere else. Greek word order is fairly flexible.

The original sentence:

• Η εξέταση της ένστασης τελειώνει σήμερα.

This is completely natural and neutral.

You could also say:

• Σήμερα τελειώνει η εξέταση της ένστασης.
• Η εξέταση της ένστασης σήμερα τελειώνει.
  This is less neutral and more marked.

Putting σήμερα at the end is very common when it simply adds time information without special emphasis.

Not always exactly. It depends on the context.

ένσταση often means:

• objection
• formal objection
• sometimes appeal in administrative or legal contexts

So in a legal or bureaucratic sentence like this, the best English word depends on the system being described. Greek learners should understand that ένσταση usually refers to some kind of formal challenge or objection.

A rough pronunciation is:

• ee ek-SE-ta-see tees EN-sta-sees te-lee-OH-nee SEE-me-ra

A more careful breakdown:

• Η = ee
• εξέταση = ek-SE-ta-see
• της = tees
• ένστασης = EN-sta-sees
• τελειώνει = te-lee-OH-nee
• σήμερα = SEE-me-ra

A couple of useful notes:

• η / ι / υ / ει / οι often sound like ee
• γγ, γκ, ντ have special sound patterns, but none of that is central here
• the accent mark shows which syllable is stressed

Because σήμερα is an adverb, meaning today.

Adverbs do not take articles the way nouns do.

So:

• σήμερα = today
• αύριο = tomorrow
• χτες / χθες = yesterday

They simply give time information to the verb:

• τελειώνει σήμερα = ends today

Yes, and it sounds a bit more formal.

Compare:

• τελειώνει σήμερα = ends today / finishes today
• ολοκληρώνεται σήμερα = is completed today / is concluded today

In official or administrative Greek, ολοκληρώνεται may sound more formal and bureaucratic.
Τελειώνει is more everyday and direct.

You know from both case and verb agreement.

• Η εξέταση is in the nominative, which is the normal case for the subject.
• της ένστασης is in the genitive, so it cannot be the subject here.
• τελειώνει is singular, matching η εξέταση.

So the structure is:

• Subject: Η εξέταση της ένστασης
• Verb: τελειώνει
• Time expression: σήμερα

Yes, it sounds fairly formal or administrative, mostly because of the nouns:

• εξέταση
• ένσταση

These are common in official, legal, academic, or bureaucratic contexts.

In everyday conversation, people might use simpler wording depending on what they mean. But the sentence itself is perfectly normal Greek and not unnaturally stiff.