Η προθεσμία υποβολής είναι αύριο.

Because υποβολής is the genitive singular form of η υποβολή.

Here, Greek uses a very common pattern:

• η προθεσμία υποβολής
• literally: the deadline of submission

So υποβολής tells you what kind of deadline it is. In English, we often use of or a noun used like an adjective:

• deadline of submission
• more natural English: submission deadline

This is one of the most useful noun patterns in Greek:

• η ώρα μαθήματος = the class hour
• το βιβλίο του παιδιού = the child’s book / the book of the child

So in this sentence, υποβολής depends on προθεσμία.

Greek can express this idea in more than one way.

The sentence you have uses a genitive noun:

• η προθεσμία υποβολής

But Greek can also use για:

• η προθεσμία για υποβολή

Both are possible. The version with the genitive often sounds a bit more compact or formal, and it is very common in official or written language.

So:

• η προθεσμία υποβολής = the submission deadline
• η προθεσμία για υποβολή = the deadline for submission

Both are good Greek, but the first one is especially typical in notices, forms, and announcements.

The subject is Η προθεσμία υποβολής.

The verb is είναι = is.

So the sentence breaks down like this:

• Η προθεσμία υποβολής = the submission deadline
• είναι = is
• αύριο = tomorrow

Greek often uses the same basic structure as English here:

• X is tomorrow

So Η προθεσμία υποβολής is the thing being talked about, and αύριο tells you when.

Because προθεσμία is a feminine singular noun, and here it is definite:

• η προθεσμία = the deadline

Without the article, προθεσμία would usually mean a deadline or just deadline in a more general sense, depending on context.

The article must match the noun in gender, number, and case:

• η προθεσμία = nominative singular feminine
• της προθεσμίας = genitive singular feminine

So η is there because the sentence means the deadline, not just a deadline.

Because αύριο here is an adverb, meaning tomorrow.

Adverbs do not take articles in this use.

So:

• είναι αύριο = is tomorrow

Compare:

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

These time words often function as adverbs and appear without an article.

There are cases where Greek can use an article with time words, but that is a different structure. In your sentence, αύριο is simply an adverb of time.

It is an adverb here.

It tells you when the deadline is. That is exactly what adverbs of time do.

In this sentence:

• Η προθεσμία υποβολής είναι αύριο
• tomorrow is not a thing; it is a time expression

So the role of αύριο is adverbial, even though in English learners sometimes expect a preposition like on or for.

Greek does not need one here.

Because this is a normal way to talk about scheduled or fixed time in both Greek and English.

Greek often uses the present tense είναι just like English says:

• The deadline is tomorrow
• not necessarily The deadline will be tomorrow

The present tense here gives a simple factual statement about the schedule.

So είναι αύριο is completely natural Greek.

Yes. Greek word order is more flexible than English word order.

The basic version is:

• Η προθεσμία υποβολής είναι αύριο.

But you could also say:

• Αύριο είναι η προθεσμία υποβολής.

That puts more emphasis on tomorrow.

In many cases, Greek changes word order for emphasis, focus, or style rather than because grammar requires it.

Still, the original order is very natural and neutral.

A rough pronunciation guide is:

• ee pro-thes-MEE-a ee-po-vo-LEES EE-ne AF-rio

A few helpful points:

• Η sounds like ee
• προθεσμία has the stress on -μία
• υποβολής has the stress on the last syllable: -λής
• είναι is pronounced roughly EE-ne
• αύριο is roughly AF-rio or AV-rio, depending on the sound environment and natural speech

The written stress marks are very important in Greek, because they show which syllable is stressed.

The dictionary form is η υποβολή.

That means:

• nominative singular: η υποβολή
• genitive singular: της υποβολής

So in your sentence, you are seeing the genitive singular form because it depends on προθεσμία.

This is very common in Greek vocabulary learning: the form you see in a sentence may not be the dictionary form.

Yes, it sounds fairly neutral to formal, and it would fit very well in official communication.

For example, you might see it in:

• an application form
• a school notice
• a university announcement
• a government website
• an email about deadlines

The nouns προθεσμία and υποβολή are both common in formal or administrative Greek.

In everyday conversation, people might also say something simpler depending on context, but this sentence is perfectly normal and natural.

Yes. Depending on context, a speaker might choose a different expression, such as:

• Η προθεσμία είναι αύριο.
  = The deadline is tomorrow.

If the context already makes clear what is being submitted, Greek may leave out υποβολής.

Another possibility is:

• Λήγει αύριο η προθεσμία υποβολής.
  = The submission deadline expires tomorrow.

That version sounds especially common in notices and announcements.

So your sentence is correct, but it is not the only natural way to express the idea.

Because it is the subject of the sentence.

The nominative is the normal case for the subject in Greek.

Here:

• Η προθεσμία υποβολής = subject
• είναι = verb
• αύριο = time expression

Since προθεσμία is the head noun of the subject, it appears in the nominative:

• η προθεσμία

Meanwhile, υποβολής is in the genitive because it depends on that noun.

Yes, literally that is very close.

But in natural English, you would usually say:

• the submission deadline
• or the deadline for submission

So the Greek structure is not always translated word-for-word into the most natural English structure.

This is a good example of why learners should pay attention to function rather than only literal translation:

• Greek: noun + genitive noun
• English: often noun + noun, or noun + for
  • noun

Προθεσμία is feminine.

You can tell from:

• the article η
• the noun ending -ία, which is very often feminine

So:

• η προθεσμία
• της προθεσμίας

Many Greek nouns ending in -ία are feminine, though of course it is always best to learn nouns together with their article.

Because Greek stress is phonemic, which means it matters for correct pronunciation and sometimes helps distinguish forms.

In your sentence:

• προθεσμία
• υποβολής

The accent shows which syllable gets the stress.

This is especially useful when a noun changes form:

• υποβολή
• υποβολής

The ending changes, and the stress placement must be written correctly too.

For learners, it is a very good habit to memorize Greek words with their accent marks.

In standard modern Greek prose, you would normally keep είναι here.

So the normal sentence is:

• Η προθεσμία υποβολής είναι αύριο.

In headlines, notes, or very compressed styles, Greek may occasionally omit words more freely, but for normal learning and normal sentences, keep the verb.

So if you are producing Greek yourself, use είναι.

Usually, yes.

Depending on context, natural English could be:

• The submission deadline is tomorrow.
• The deadline for submission is tomorrow.
• The due date is tomorrow.
  if the context is assignments or required work

So the exact English wording can vary, but the Greek structure remains the same.

For learning Greek grammar, the key point is that:

• προθεσμία is the main noun
• υποβολής specifies what the deadline is for
• αύριο tells you when