Learn Hardcore Greek: Ο φίλος μου λέει ότι ο καφές σήμερα είναι πολύ καλός. - My friend says that the coffee today is very good.

English usually drops the in these cases, but Greek keeps it. So ο φίλος μου literally looks like the friend of me, but it simply means my friend.

Why is μου after φίλος and not before, like μου φίλος?

Short possessive pronouns such as μου, σου, του, της, μας, σας, τους normally come after the noun, not before it:

ο φίλος μου = my friend
η αδελφή σου = your sister
το βιβλίο του = his book

Putting μου before the noun (μου φίλος) is not standard Greek; it sounds wrong.

If you want to emphasize my, you use a different structure:

ο δικός μου φίλος = my friend (as opposed to someone else’s)

But even there, μου still follows δικός.

Why do some words have an accent mark (like φίλος, καφές, πολύ) while others (like μου, ο) do not?

Modern Greek uses one accent mark (τόνος) to show which syllable is stressed in a word:

φίλος (stress on φί)
καφές (stress on φές)
σήμερα (stress on σήμε)
είναι (stress on εί)
πολύ (stress on λύ)
καλός (stress on λός)

Very short, unstressed words called clitics are written without an accent:

μου, σου, του, της, μας, σας, τους
ο, η, το (the articles)
θα, να, δεν, δε, μη(ν), σε

So μου and ο have no accent because they are unstressed.

In your sentence:

Ο is just the capital form of the unstressed article ο, so it also has no accent.
Content words like φίλος, λέει, ότι, καφές, σήμερα, είναι, πολύ, καλός all carry an accent mark to show where the stress falls.

What exactly is λέει here, and how do you pronounce it?

λέει is the 3rd person singular, present tense of the verb λέω (to say).

The present tense forms are:

(εγώ) λέω – I say
(εσύ) λες – you say
(αυτός/αυτή/αυτό) λέει – he/she/it says
(εμείς) λέμε – we say
(εσείς) λέτε – you (pl./formal) say
(αυτοί/αυτές/αυτά) λένε – they say

Pronunciation of λέει:

Two vowel sounds: λέ-ει
Roughly like LEH-ee in English, with the stress on the first part: λέει.

What does ότι do in this sentence, and how is it different from πως or ό,τι?

Here ότι is a conjunction meaning that. It introduces a clause that is the content of what someone says, thinks, knows, etc.:

Ο φίλος μου λέει ότι ο καφές σήμερα είναι πολύ καλός.
= My friend says that the coffee today is very good.

Key points:

ότι vs πως
- After verbs like λέω, νομίζω, ξέρω, πιστεύω, you can usually use either:
  - Λέει ότι ο καφές είναι καλός.
  - Λέει πως ο καφές είναι καλός.
- Both are common; πως is often a bit more informal.
ότι vs ό,τι
- ότι (no comma) = that (conjunction, as here).
- ό,τι (with comma) = whatever / anything that (a pronoun):
  - Φάε ό,τι θέλεις. = Eat whatever you want.
- In your sentence you need ότι, not ό,τι.
Can you omit ότι like English often omits that?
- English: My friend says (that) the coffee is very good.
- Greek normally keeps ότι/πως:
  - Ο φίλος μου λέει ότι ο καφές είναι πολύ καλός.
- In very casual speech you might sometimes hear it dropped, but the safe, standard choice is to include ότι (or πως).

Why is there another ο before καφές? Could we say λέει ότι καφές σήμερα είναι πολύ καλός?

You normally need the article with a concrete noun used as a subject:

ο καφές είναι καλός = the coffee is good / coffee is good
η μπύρα είναι κρύα = the beer is cold
το φαγητό είναι έτοιμο = the food is ready

So in your sentence:

λέει ότι ο καφές σήμερα είναι πολύ καλός is the natural version.
λέει ότι καφές σήμερα είναι πολύ καλός sounds ungrammatical or at best very strange in normal Greek.

Greek uses the definite article more than English does, especially with known, specific things (like today’s coffee).

Can σήμερα be moved to a different place in the sentence?

Yes. Greek word order is flexible, especially for adverbs like σήμερα. All of these are grammatical, with slightly different emphasis:

Ο φίλος μου λέει ότι ο καφές σήμερα είναι πολύ καλός.
(Fairly neutral; σήμερα loosely connected to ο καφές.)
Ο φίλος μου λέει ότι σήμερα ο καφές είναι πολύ καλός.
(Emphasis that today the coffee is very good; maybe it wasn’t on other days.)
Σήμερα ο φίλος μου λέει ότι ο καφές είναι πολύ καλός.
(Emphasis on today as the time when he says this.)
Ο φίλος μου λέει ότι ο καφές είναι πολύ καλός σήμερα.
(Very natural; σήμερα at the end, modifying the whole statement.)

So σήμερα can appear near the beginning, before or after ο καφές, or at the end. The sentence remains correct; only the nuance of focus changes.

Do we have to include είναι, or can we say ο καφές σήμερα πολύ καλός?

In normal, full sentences you include είναι:

Ο καφές σήμερα είναι πολύ καλός. = The coffee today is very good.

Leaving out είναι:

Ο καφές σήμερα πολύ καλός

would sound like a headline, a note, or very telegraphic/poetic language, not like standard spoken or written Greek.

The verb είναι is the 3rd person singular of είμαι (to be), and in regular sentences you should keep it.

Why is it πολύ καλός and not πολύ καλά?

Here πολύ is an adverb meaning very, and καλός is an adjective agreeing with ο καφές (masculine, singular, nominative).

ο καφές είναι καλός = the coffee is good
ο καφές είναι πολύ καλός = the coffee is very good

Important points:

πολύ as an adverb is invariable – it does not change for gender or number.
- πολύ καλός καφές
- πολύ καλή μπύρα
- πολύ καλό τσάι
καλός must match ο καφές: masculine singular.
- καλός (masc. sg.)
- καλή (fem. sg.)
- καλό (neut. sg.)
καλά is mostly:
- an adverb meaning well (e.g. Μιλάει καλά ελληνικά. = He/She speaks Greek well), or
- a neuter plural adjective (καλά παιδιά = good children).

So πολύ καλά would not fit here, because you need an adjective agreeing with ο καφές, not an adverb or neuter plural form.

Why does καλός end in -ός? Would it change with a different noun?

Yes, καλός changes form to agree with the noun’s gender and number. The basic singular forms are:

Masculine: καλός
- ο καφές είναι καλός = the coffee is good
Feminine: καλή
- η μπύρα είναι καλή = the beer is good
Neuter: καλό
- το τσάι είναι καλό = the tea is good

So:

ο καφές σήμερα είναι πολύ καλός
η μπύρα σήμερα είναι πολύ καλή
το τσάι σήμερα είναι πολύ καλό

Greek adjectives must agree with the noun in gender, number, and case. In your sentence the subject is masculine singular nominative (ο καφές), so the adjective is καλός.

Could we say Ο φίλος μου μου λέει ότι ο καφές σήμερα είναι πολύ καλός? Would that be correct?

Yes, that is correct, but the meaning changes slightly.

Ο φίλος μου λέει ότι ο καφές σήμερα είναι πολύ καλός.
= My friend says that the coffee today is very good.
(No information about to whom he is saying this.)
Ο φίλος μου μου λέει ότι ο καφές σήμερα είναι πολύ καλός.
= My friend tells me that the coffee today is very good.
(Now we know he is saying it to me.)

Here:

The first μου is possessive: ο φίλος μου = my friend.
The second μου is an indirect object pronoun: μου λέει = he says to me.

Greek often uses these short pronouns (like μου) before the verb to show to whom or for whom something is done.