Learn Hardcore Greek: Η μέρα είναι όμορφη σήμερα.

In natural English, we’re more likely to say: “It’s a beautiful day today.”
So the meaning matches, but Greek keeps “the day” as the subject instead of using “it” like English does.

Why do we use the article Η here? In English we just say “It’s a beautiful day,” not “The day is beautiful.”

Greek uses the definite article much more often than English, especially:

with general statements: Η μέρα είναι ωραία. = The day is nice / Days are nice (in general).
with parts of the day, weather, time, body parts, etc.

In Η μέρα είναι όμορφη σήμερα, the article Η is natural and almost required.
Saying just Μέρα είναι όμορφη σήμερα would sound unnatural or wrong in standard modern Greek.

Even though English prefers “It’s a beautiful day today” (with no “the”), Greek comfortably says “Η μέρα είναι όμορφη σήμερα” with Η.

How do I know that μέρα is feminine, and why does that matter?

You learn the gender as part of the noun:

η μέρα = the day (feminine)
ο καιρός = the weather (masculine)
το σπίτι = the house (neuter)

Gender matters because:

The article must agree:
- η μέρα (fem.)
- ο ήλιος (masc.)
- το δέντρο (neut.)
The adjective must agree:
- όμορφη μέρα (fem.)
- όμορφος καιρός (masc.)
- όμορφο σπίτι (neut.)

In our sentence:

η μέρα → feminine
so the adjective must be feminine: όμορφη (not όμορφος, not όμορφο).

That’s why we say Η μέρα είναι όμορφη and not Η μέρα είναι όμορφος.

Why is the adjective όμορφη after είναι and not before the noun, like η όμορφη μέρα?

Greek distinguishes two main uses of adjectives:

Predicative position (after the verb “to be”):
- Η μέρα είναι όμορφη.
  = The day is beautiful. (Describing the state of the day.)
Attributive position (before the noun with the article):
- Η όμορφη μέρα ήταν χτες.
  = The beautiful day was yesterday. (Which day? The beautiful one.)

In Η μέρα είναι όμορφη σήμερα we’re describing today’s day, not identifying a specific “beautiful day” as an item among others. So the natural structure is:

subject: Η μέρα
verb: είναι
predicative adjective: όμορφη

You can make an attributive version for a slightly different sentence:

Σήμερα είναι μια όμορφη μέρα.
= Today is a beautiful day. (Focusing on “a beautiful day” as a unit.)

Can the word σήμερα go somewhere else in the sentence, or must it stay at the end?

σήμερα (today) is an adverb, and adverbs are fairly flexible in Greek word order. All of these are correct:

Η μέρα είναι όμορφη σήμερα.
Σήμερα η μέρα είναι όμορφη.
Η μέρα σήμερα είναι όμορφη.

The differences are mostly about emphasis:

Σήμερα η μέρα είναι όμορφη.
Slight extra focus on “today (as opposed to other days)”.
Η μέρα είναι όμορφη σήμερα.
More neutral; very common.
Η μέρα σήμερα είναι όμορφη.
Also possible; can sound a bit more “spoken” or contrastive (“The day today is beautiful (unlike yesterday)”).

So no, σήμερα does not have to be at the end.

Could I say Σήμερα είναι μια όμορφη μέρα instead? Does it mean the same thing?

Yes, and it’s very natural. Nuance:

Η μέρα είναι όμορφη σήμερα.
Literally: The day is beautiful today.
Common translation: It’s a beautiful day today.
Σήμερα είναι μια όμορφη μέρα.
Literally: Today is a beautiful day.
Also: It’s a beautiful day today.

Difference:

Η μέρα είναι όμορφη σήμερα speaks more about “the day (today) as it is.”
Σήμερα είναι μια όμορφη μέρα highlights “Today is *one beautiful day (among many possible days).”*

In everyday speech, both are fine and will usually be understood as the same idea.

What’s the difference between talking about η μέρα and ο καιρός when describing how nice it is outside?

Both are used, but with slightly different focuses:

Η μέρα είναι όμορφη σήμερα.
Literally: The day is beautiful today.
This is a bit more general or poetic: the whole “day” is nice.
Ο καιρός είναι όμορφος σήμερα.
Literally: The weather is beautiful today.
This focuses specifically on the weather (sun, temperature, sky).

Common alternatives with καιρός:

Ο καιρός είναι καλός σήμερα. = The weather is good today.
Έχει πολύ καλό καιρό σήμερα. = The weather is very good today.

So η μέρα sounds a bit broader or more “day as an experience,” and ο καιρός is more strictly “weather.”

Does είναι mean “is” or “are”? Why doesn’t it change?

είναι is the 3rd person singular and plural form of the verb είμαι (to be):

είμαι = I am
είσαι = you are (singular)
είναι = he / she / it is
είμαστε = we are
είστε = you are (plural / polite)
είναι = they are

So είναι can mean:

is (He is, She is, It is, The day is)
or are (They are)

Context tells you which.
In Η μέρα είναι όμορφη, the subject η μέρα is singular, so είναι means “is.”

How do you pronounce Η μέρα είναι όμορφη σήμερα?

Approximate pronunciation (stress is on the bolded syllable):

Η → /i/
μέρα → ME-ra → /ˈme.ra/
είναι → I-ne → /ˈi.ne/
όμορφη → O-mor-fi → /ˈo.mor.fi/
σήμερα → SI-me-ra → /ˈsi.me.ra/

All together (rough guide):
i ME-ra I-ne O-mor-fi SI-me-ra

Key points:

The letter η is pronounced /i/, like English “ee” in see.
The combination εί is also pronounced /i/.
Each Greek word has one main stress (shown by the accent mark).

What’s the difference between Η and ή that I sometimes see?

They are different words:

η (lowercase, no accent)
= the feminine article “the” (as in η μέρα, η πόρτα).
ή (with an accent)
= the conjunction “or”:
Θέλεις καφέ *ή τσάι;* = Do you want coffee or tea?

At the start of a sentence, the article is capitalized: Η.
So in Η μέρα είναι όμορφη σήμερα, Η is just the capitalized form of η = the (feminine).

Can Greek drop words here, like just saying Όμορφη μέρα σήμερα!?

Yes. In informal speech or in writing like headlines or captions, you’ll often see shortened versions:

Όμορφη μέρα σήμερα! = Beautiful day today!
Τι όμορφη μέρα σήμερα! = What a beautiful day today!

What’s going on:

The article η and the verb είναι are omitted.
The meaning is still clearly understood as “(It’s a) beautiful day today!”

This is very natural in spoken Greek, especially as an exclamation.

Could I use another adjective instead of όμορφη, like ωραία? Is there a difference?

Yes, you often hear:

Η μέρα είναι ωραία σήμερα.
Σήμερα είναι μια ωραία μέρα.

όμορφη and ωραία both can mean “beautiful / nice,” but:

όμορφη tends slightly more toward “beautiful” (visual / aesthetic).
ωραία is very common and can mean nice, pleasant, great as well as beautiful.

In everyday talk about the day or the weather, ωραία might even be more frequent:

Ο καιρός είναι ωραίος σήμερα. = The weather is nice today.
Τι ωραία μέρα! = What a nice/beautiful day!

In your sentence, Η μέρα είναι όμορφη σήμερα and Η μέρα είναι ωραία σήμερα are both natural and very close in meaning.