Learn Hardcore Greek: Σήμερα είναι πολύ όμορφη μέρα.

Greek does have an indefinite article (ένας, μια, ένα), but it is very often left out in sentences with είμαι / είναι when you are simply describing what something is.

So instead of literally saying Σήμερα είναι μια πολύ όμορφη μέρα, Greek can just say Σήμερα είναι πολύ όμορφη μέρα and it still means Today is a very beautiful day.
The structure [subject] + είναι + [adjective + noun] often does not need ένας / μια / ένα when it’s a general description.

If I say Σήμερα είναι μια πολύ όμορφη μέρα, does the meaning or feeling change?

Yes, it is also correct, and many speakers actually say it this way very often.

Σήμερα είναι πολύ όμορφη μέρα. – neutral description: Today is a very beautiful day.
Σήμερα είναι μια πολύ όμορφη μέρα. – almost the same, but μια can make it feel a bit more like what a very beautiful day (this is) or today is one very beautiful day – slightly more vivid or emphatic.

In everyday conversation, both versions sound natural; the difference is small and mostly about nuance, not grammar.

Why does όμορφη end in -η and not in -ος?

Adjectives in Greek must agree with the noun in gender, number, and case.

The basic forms of this adjective are:

όμορφος – masculine
όμορφη – feminine
όμορφο – neuter

Since μέρα (day) is a feminine noun, you need the feminine form of the adjective: όμορφη μέρα, not όμορφος μέρα or όμορφο μέρα.

Why is it πολύ όμορφη and not πολλή όμορφη? What is πολύ grammatically?

Here πολύ is an adverb meaning very, and as an adverb it is invariable: it always stays πολύ, it does not change for gender, number, or case.

πολύ όμορφη μέρα = very beautiful day (adverb + adjective)

When πολύς / πολλή / πολύ is an adjective meaning much / many / a lot of, then it does change:

πολύς χρόνος – much time (masc.)
πολλή δουλειά – a lot of work (fem.)
πολύ νερό – a lot of water (neut.)

In your sentence, πολύ modifies the adjective όμορφη, so it is the adverb form and stays πολύ.

What exactly does πολύ do in this sentence, and where should it go?

πολύ here intensifies the adjective όμορφη, so it means very beautiful.

The normal position is before the adjective:
πολύ όμορφη μέρα = a very beautiful day.

You might see other orders in poetic or very emphatic language (for example, Πολύ όμορφη μέρα είναι σήμερα), but for everyday speech, keep πολύ immediately before the adjective.

What is the difference between μέρα and ημέρα?

Both mean day and are feminine nouns, but:

μέρα is the everyday, colloquial form.
ημέρα is more formal, learned, or used in set expressions (administrative language, some compounds, etc.).

In a casual sentence like Σήμερα είναι πολύ όμορφη μέρα, using ημέρα would sound too formal or old‑fashioned for normal conversation.

How do you pronounce Σήμερα είναι πολύ όμορφη μέρα?

A simple phonetic approximation (for an English speaker) is:

Σήμερα – SEE-me-ra
είναι – EE-ne
πολύ – po-LEE
όμορφη – O-mor-fi (stress on O)
μέρα – ME-ra

In IPA: [ˈsimera ˈine poˈli ˈomorfi ˈmera]

Note in particular:

Greek η (in Σήμερα, είναι, όμορφη) is pronounced like English ee.
The digraph αι (in μέρα) is pronounced like e in bed.

The written accent (´) shows which syllable is stressed.

Can I change the word order? For example, can I say Είναι πολύ όμορφη μέρα σήμερα?

Yes. Greek word order is relatively flexible, and several versions are natural:

Σήμερα είναι πολύ όμορφη μέρα. – neutral, slight focus on today.
Είναι πολύ όμορφη μέρα σήμερα. – also natural; similar meaning, a bit more like It’s a very beautiful day today.
Πολύ όμορφη μέρα είναι σήμερα. – puts more emphasis on πολύ όμορφη; more expressive or literary.
Σήμερα η μέρα είναι πολύ όμορφη. – explicitly makes η μέρα the subject: Today the day is very beautiful.

All are grammatically correct; the differences are mainly about emphasis and style.

What case is μέρα in here, and why?

μέρα is in the nominative singular feminine.

With the verb είμαι / είναι (to be), both the subject and the noun that describes the subject (the predicate noun) are in the nominative case:

Η μέρα είναι όμορφη. – η μέρα (subject) and όμορφη (predicate adjective) are in nominative.
Σήμερα είναι πολύ όμορφη μέρα. – the thing being described is μέρα, so it appears in nominative too.

So Greek does not use the accusative after είναι in this kind of sentence.

Can I drop είναι and just say Σήμερα πολύ όμορφη μέρα?

In a normal full sentence, you should keep είναι; leaving it out sounds incomplete or very telegraphic.

However, in exclamations, headlines, or very informal notes, Greek can omit the verb:

Τι όμορφη μέρα σήμερα! – What a beautiful day today!
On a photo caption: Πολύ όμορφη μέρα στη θάλασσα! – A very beautiful day at the sea!

So for regular sentences you would say Σήμερα είναι πολύ όμορφη μέρα, but in short exclamations you can drop είναι.

Is there a difference between saying όμορφη μέρα and ωραία μέρα?

Both are very common and both can translate as beautiful / nice day, but there is a slight nuance:

όμορφη μέρα – literally beautiful day, with a bit more focus on beauty/pleasantness.
ωραία μέρα – nice / fine day, very common in casual speech for good weather or a pleasant day.

In most everyday situations they are interchangeable, and choosing one or the other is often just a matter of personal style.