Learn Hardcore Greek: Ο Έλληνας μιλάει ελληνικά στο σπίτι.

In Greek, singular countable nouns almost always take a definite article when they’re used as subjects or objects, even where English would often drop it.

Ο Έλληνας literally means “the Greek (man)”.
Without context, it sounds like you’re talking about a specific person, not “Greeks in general.”

Some patterns:

With article (subject/object):
- Ο γιατρός είναι εδώ. = The doctor is here.
- Ο Έλληνας μιλάει ελληνικά. = The Greek (man) speaks Greek.
Without article when it’s a predicate after “to be”:
- Είναι Έλληνας. = He is Greek.
- Είμαι γιατρός. = I am a doctor.

So the article Ο is normal Greek grammar for a noun used as the subject, even if English might not use “the.”

Why is Έλληνας capitalized but ελληνικά is not?

Greek capitalization rules are different from English:

Nationality as a person (noun): capitalized
- Έλληνας, Ελληνίδα = Greek (man, woman)
- Γάλλος, Γαλλίδα = French (man, woman)
Language names: not capitalized
- ελληνικά = Greek (language)
- γαλλικά = French (language)
- αγγλικά = English (language)

So in your sentence:

Ο Έλληνας – capitalized because it’s a person/nationality noun.
ελληνικά – lower-case because it’s the name of a language.

Why is it ελληνικά and not something like ελληνική or ελληνικό?

ελληνικά here is the language and grammatically it is:

neuter
plural
accusative case

Greek typically uses the neuter plural form to name languages:

ελληνικά – Greek
αγγλικά – English
γαλλικά – French
ισπανικά – Spanish

The forms you mentioned are adjectives, not the language as a noun:

ελληνικός / ελληνική / ελληνικό = Greek (as an adjective)
- ελληνική γλώσσα = Greek language
- ελληνικό φαγητό = Greek food

In your sentence, μιλάει ελληνικά literally means “he speaks Greek (things/words)”, which is why the neuter plural is used.

What is the difference between μιλάει and μιλά? Are both correct?

The verb is μιλάω (to speak), which belongs to a group of verbs that historically had two parallel forms:

μιλάω → 3rd person singular: μιλάει
μιλώ → 3rd person singular: μιλά

In modern Greek:

μιλάει and μιλά are both correct and mean the same thing.
μιλάει sounds a bit more colloquial or full,
μιλά is a bit more compact and sometimes a bit more formal, but both are used everywhere.

So you can say either:

Ο Έλληνας μιλάει ελληνικά στο σπίτι.
Ο Έλληνας μιλά ελληνικά στο σπίτι.

No difference in meaning.

Where is the subject pronoun “he”? Why don’t we see αυτός?

Greek is a “pro-drop” language: subject pronouns are usually omitted because the verb ending already tells you who the subject is.

μιλάει clearly shows 3rd person singular (he/she/it speaks).
So you normally just say: Μιλάει ελληνικά. = He/She speaks Greek.

You only add the pronoun αυτός / αυτή / αυτό when you want to:

emphasize the subject:
- Αυτός μιλάει ελληνικά, όχι εγώ. = He speaks Greek, not me.
contrast people:
- Αυτός μιλάει ελληνικά, αυτή μιλάει αγγλικά.

So in Ο Έλληνας μιλάει ελληνικά στο σπίτι, the noun Ο Έλληνας already fills the role of “he,” so no pronoun is needed.

What exactly does στο mean? Is it one word?

στο is a contraction of:

σε (preposition: in, at, to)
το (neuter singular definite article: the)

So:

σε + το σπίτι → στο σπίτι = in/at the house / at home

Other common contractions:

σε + τον → στον (masc.)
σε + την → στη(ν) (fem.)
σε + τους → στους (masc. plural)
σε + τις → στις (fem. plural)

In your sentence, στο σπίτι means “at home / in the house”.

Is there an article with σπίτι, or is it just “home” without “the”?

There is an article; it’s just hidden inside στο.

στο σπίτι = σε + το σπίτι = in/at the house → often translated as at home.

Compare:

Πηγαίνω σπίτι. = I’m going home. (no article, more like an adverb “home”)
Πηγαίνω στο σπίτι. = I’m going to the house / I’m going home (to the house).

In your sentence μιλάει ελληνικά στο σπίτι, the literal structure is “he speaks Greek in-the house”, but in natural English we usually say “at home.”

Could I change the word order, for example: Ο Έλληνας στο σπίτι μιλάει ελληνικά?

Yes, Greek word order is more flexible than English, but changes in order can slightly change the emphasis.

All of these are grammatical:

Ο Έλληνας μιλάει ελληνικά στο σπίτι.
- Neutral: The Greek (man) speaks Greek at home.
Ο Έλληνας στο σπίτι μιλάει ελληνικά.
- Slight emphasis that “at home” is the place where this happens, maybe contrasting with another place.
Στο σπίτι ο Έλληνας μιλάει ελληνικά.
- Emphasizes “at home” (as opposed to somewhere else).
Ελληνικά μιλάει ο Έλληνας στο σπίτι.
- Emphasis on “Greek”; e.g. he might speak another language elsewhere.

Basic idea: the closer to the front a phrase moves, the more emphasized or contrastive it often becomes.

How do I say this for a woman instead of a man? Is Έλληνας always masculine?

Έλληνας is specifically masculine: Greek man.
The feminine form is Ελληνίδα (Greek woman).

So:

Ο Έλληνας μιλάει ελληνικά στο σπίτι.
= The Greek man speaks Greek at home.
Η Ελληνίδα μιλάει ελληνικά στο σπίτι.
= The Greek woman speaks Greek at home.

Article + noun:

Ο Έλληνας (masc.)
Η Ελληνίδα (fem.)

For plural:

Οι Έλληνες μιλάνε ελληνικά στο σπίτι. = The Greeks speak Greek at home. (group of men or mixed)
Οι Ελληνίδες μιλάνε ελληνικά στο σπίτι. = The Greek women speak Greek at home.

Which cases are used in this sentence? How do the forms change?

The sentence is:

Ο Έλληνας μιλάει ελληνικά στο σπίτι.

Cases:

Ο Έλληνας – nominative singular masculine
- Subject of the verb μιλάει.
ελληνικά – accusative (neuter plural form, used as the language name)
- Direct object of μιλάει.
στο σπίτι – accusative after a preposition
- στο = σε + το, and σπίτι is neuter singular accusative.
- In Greek, nouns after prepositions usually appear in the accusative.

So overall:
Nominative for the subject, accusative for the object and prepositional phrase.

Does μιλάει mean “he speaks (in general)” or “he is speaking (right now)”?

Modern Greek doesn’t separate simple present and present continuous the way English does. The present tense can mean both:

Habitual / general truth:
- Ο Έλληνας μιλάει ελληνικά στο σπίτι.
  = The Greek (man) speaks Greek at home (as a habit).
Right now (with context):
- If someone asks “Τώρα τι κάνει;” (What is he doing now?)
  and you answer Μιλάει ελληνικά στο σπίτι,
  it can mean He is speaking Greek at home (right now).

Context or adverbs like τώρα (now), συνήθως (usually), etc., show which meaning is intended. The verb form μιλάει itself doesn’t change.