Learn Hardcore Greek: Έχω δέκα βιβλία στο σπίτι.

In modern Greek, dictionaries usually list verbs in this 1st person singular present form (here: έχω), not with an infinitive like in English.

Where is the word for I in this sentence? Why isn’t εγώ written?

The subject I is understood from the verb ending, so it doesn’t need to be written.

Έχω δέκα βιβλία στο σπίτι.
Literally: Have ten books at home.
But because έχω clearly shows 1st person singular, it means I have.

You can add the pronoun for emphasis:

Εγώ έχω δέκα βιβλία στο σπίτι.
This means I have ten books at home, with emphasis on I (as in: I have them, not someone else).

Greek is a “pro‑drop” language: subject pronouns (εγώ, εσύ, αυτός, etc.) are often dropped unless you want to stress them or avoid ambiguity.

Why is there no article like a or the before δέκα βιβλία?

In Greek, when you use a cardinal number directly before a plural noun, you normally do not use a definite article:

δέκα βιβλία → ten books
τρεις φίλοι → three friends
πέντε μέρες → five days

There is also no separate word for a/an in the plural in Greek, just like in English (a book but books). So δέκα βιβλία naturally corresponds to ten books, not the ten books.

If you add the definite article, the meaning changes:

τα δέκα βιβλία → the ten books (a specific set of ten books)

So:

Έχω δέκα βιβλία στο σπίτι. → I have ten books at home.
Έχω τα δέκα βιβλία στο σπίτι. → I have the ten books at home (those particular ten we both know about).

What case are βιβλία and σπίτι in here, and why do they look like that?

Both βιβλία and σπίτι are in the accusative case in this sentence.

βιβλία
- Singular: το βιβλίο (the book)
  - Nominative: το βιβλίο
  - Accusative: το βιβλίο
- Plural: τα βιβλία (the books)
  - Nominative: τα βιβλία
  - Accusative: τα βιβλία
For neuter nouns, nominative and accusative look the same in both singular and plural.
In our sentence, βιβλία is the direct object of έχω, so it is accusative, but its form is identical to the nominative.
σπίτι
- Singular: το σπίτι (the house, home)
  - Nominative: το σπίτι
  - Accusative: το σπίτι
After the preposition σε (in, at, to), Greek uses the accusative case. In στο σπίτι, σπίτι is accusative, but again, because it’s neuter, it looks exactly like the nominative.

What exactly does στο mean, and why isn’t it written as σε το σπίτι?

στο is a contraction of:

σε (in, at, to) + το (the, neuter singular)

So:

σε + το σπίτι → στο σπίτι

This contraction is standard and almost always used in speech and writing. Similar contractions are:

σε + τον → στον (for masculine nouns)
- στον φίλο (to the friend, at the friend)
σε + την → στη(ν) (for feminine nouns)
- στη μητέρα (at the mother, to the mother)

In our sentence:

στο σπίτι means at home / in the house, depending on context. Often, στο σπίτι is best translated as at home in natural English.

Can I change the word order, for example say Στο σπίτι έχω δέκα βιβλία? Does it change the meaning?

Yes, Greek word order is quite flexible, and several versions are possible:

Έχω δέκα βιβλία στο σπίτι.
Στο σπίτι έχω δέκα βιβλία.
Δέκα βιβλία έχω στο σπίτι.

They all basically mean I have ten books at home, but the emphasis shifts:

Έχω δέκα βιβλία στο σπίτι.
Fairly neutral: stating what you have and where.
Στο σπίτι έχω δέκα βιβλία.
Slight emphasis on στο σπίτι (at home), as if contrasting with somewhere else:
- At home I have ten books (maybe somewhere else I have more or fewer).
Δέκα βιβλία έχω στο σπίτι.
Slight emphasis on δέκα βιβλία (ten books), often used when stressing the number.

The basic grammatical roles don’t change; only the focus does.

How is the whole sentence pronounced?

One fairly standard pronunciation (IPA) is:

Έχω δέκα βιβλία στο σπίτι.
[ˈe.xo ˈðe.ka viˈvli.a sto ˈspi.ti]

Some key points for an English speaker:

χ in έχω is a voiceless velar fricative, like the ch in German Bach or Scottish loch.
β is pronounced like English v, not like b. So βιβλία is roughly viv‑LEE‑a.
η, ι, υ, ει, οι, υι are all pronounced like ee in English see (here: βιβλία, σπίτι).
Stress is marked by the accent: Έχω, δέκα, βιβλία, σπίτι each have one stressed syllable.

Why is it δέκα βιβλία and not βιβλία δέκα?

In Greek, cardinal numbers (one, two, three, ten, etc.) almost always come before the noun:

δέκα βιβλία → ten books
τρεις μέρες → three days
τέσσερις καρέκλες → four chairs

The order βιβλία δέκα is possible only in very marked or poetic contexts, and would sound unusual or emphatic in everyday speech, often adding a special nuance (e.g. books, ten in number).

So in normal modern Greek, you should place the number before the noun.

What is the singular of βιβλία, and how is this plural formed?

The singular is:

το βιβλίο → the book

The plural is:

τα βιβλία → the books

βιβλίο → βιβλία is a common neuter pattern:

neuter singular in ‑ο
neuter plural in ‑α

More examples:

το παιδί → τα παιδιά (the child → the children)
το ποτήρι → τα ποτήρια (the glass → the glasses)
το γράμμα → τα γράμματα (the letter → the letters)

Note that in βιβλίο → βιβλία, the stress stays on the same syllable: βιβλίο, βιβλία.

Does Έχω here mean specifically simple present (I have) or can it also mean I am having?

Greek has one present tense form (έχω) that usually covers both simple and continuous meanings in English:

Έχω δέκα βιβλία στο σπίτι.
Can correspond to:
- I have ten books at home.
  (simple statement of fact)

In context, it could also imply something like I currently have ten books at home, but Greek doesn’t distinguish I have vs I am having with different verb forms the way English does. The present tense in Greek is generally imperfective (ongoing / habitual), and the exact nuance is understood from context, not from a separate continuous form.