Η πρώτη όπτηση είναι αύριο.

Η is the feminine singular definite article, so it means the.

It is used because όπτηση is a feminine singular noun. So:

• η όπτηση = the firing / the baking / the heat treatment
• η πρώτη όπτηση = the first firing

Because πρώτη has to agree with όπτηση.

In Greek, adjectives change form to match the noun in:

• gender
• number
• case

Here, όπτηση is:

• feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• πρώτος = masculine
• πρώτη = feminine
• πρώτο = neuter

So η πρώτη όπτηση means the first firing.

Όπτηση is a noun. It usually means something like:

• firing
• baking
• roasting
• calcination
• more generally, heating a material at high temperature, depending on the context

It is a somewhat technical or specialized word in many contexts, such as:

• ceramics
• metallurgy
• chemistry
• industrial processing

Grammatically, it is a feminine noun.

Είναι means is.

The sentence structure is very similar to English:

• Η πρώτη όπτηση = The first firing
• είναι = is
• αύριο = tomorrow

So the full sentence means:

• The first firing is tomorrow.

Greek normally keeps the verb είναι in this kind of sentence, unlike some languages where the present-tense to be can be dropped.

Αύριο means tomorrow.

Here it functions as a time expression, telling you when something happens.

So:

• είναι αύριο = is tomorrow

Greek often uses time words this way, without needing a preposition. English does the same in this sentence.

This is a very natural, neutral Greek word order:

• subject: Η πρώτη όπτηση
• verb: είναι
• time expression: αύριο

Greek word order is more flexible than English, because endings and articles give more grammatical information. So you may also hear variations such as:

• Αύριο είναι η πρώτη όπτηση.
• Η πρώτη όπτηση αύριο είναι. (less neutral, more marked in tone)

But Η πρώτη όπτηση είναι αύριο is straightforward and standard.

In most ordinary contexts, η is expected here.

• Η πρώτη όπτηση είναι αύριο. = the normal way to say The first firing is tomorrow.

If you remove the article, the sentence sounds less standard or more like a heading, note, label, or very compressed style. Greek generally uses the definite article more regularly than English does in many situations.

So for a normal full sentence, keep η.

No. The subject is Η πρώτη όπτηση.

You can tell because:

• it has the article η
• the adjective and noun form a noun phrase
• semantically, that is the thing being talked about

Αύριο is just an adverbial time expression meaning tomorrow.

So the structure is:

• Subject: Η πρώτη όπτηση
• Verb: είναι
• Time expression / adverbial: αύριο

A rough pronunciation is:

ee PROH-tee OP-tee-see EE-neh AV-rio

A slightly more careful breakdown:

• Η = ee
• πρώτη = PROH-tee
• όπτηση = OP-tee-see
• είναι = EE-ne
• αύριο = AV-rio

A few useful notes:

• η is pronounced like ee
• ω and ο are both pronounced o in Modern Greek
• πτ in όπτηση is pronounced clearly, though in fast speech consonant clusters may sound smoother
• αύ is usually pronounced av before a voiced sound, so αύριο sounds like AV-rio

Greek uses accent marks to show which syllable is stressed.

In this sentence:

• πρώτη → stress on πρώ-
• όπτηση → stress on όπ-
• είναι → stress on εί-
• αύριο → stress on αύ-

These marks are important in writing, because stress is phonemic in Greek and can help distinguish words or correct pronunciation.

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

You can think of it this way:

• η = nominative feminine singular article
• πρώτη = nominative feminine singular adjective
• όπτηση = nominative feminine singular noun

So the whole phrase is a nominative subject phrase.

Yes. That would mean:

• The first firing will be tomorrow.

Adding θα makes the sentence explicitly future.

But Greek often uses the present tense with a future time word like αύριο, especially for scheduled or certain future events. So:

• Η πρώτη όπτηση είναι αύριο. = perfectly natural
• Η πρώτη όπτηση θα είναι αύριο. = also natural, a bit more explicitly future

Both are correct; the first one is very common for arrangements and schedules.

The grammar is neutral and standard. The only thing that may sound specialized is the noun όπτηση.

So:

• the sentence structure is ordinary Greek
• the vocabulary may be technical depending on context

For example, in ceramics, engineering, chemistry, or manufacturing, όπτηση is a very normal term. Outside those contexts, many learners may not encounter it early.

Yes, quite closely:

• Η = the
• πρώτη = first
• όπτηση = firing
• είναι = is
• αύριο = tomorrow

So the sentence maps very neatly onto English:

• The first firing is tomorrow.

This is a good example of a Greek sentence whose basic structure is very similar to English.