Learn Hardcore Greek: Το βιβλίο που διαβάζεις είναι φθηνό.

που introduces a relative clause, equivalent to English that/which/who. It is invariable (it doesn’t change for gender, number, or case). Note the difference between unaccented που (relative) and accented πού (interrogative/adverb meaning where).

Can I omit που, like in English (the book you’re reading)?

No. In Greek you normally need που to introduce the relative clause: Το βιβλίο που διαβάζεις. Omitting it is ungrammatical in standard Greek.

Why is it Το (the definite article) and not Ένα?

Because the relative clause που διαβάζεις specifies a particular book, so Greek uses the definite article Το. Ένα βιβλίο που διαβάζεις would mean a/one book that you read, which suggests some unspecified book and sounds odd here.

Is Το βιβλίο nominative or accusative? It seems to be the object of διαβάζεις.

Το βιβλίο is nominative because it’s the subject of the main clause (είναι φθηνό). Inside the relative clause, there is a gap after που where the object of διαβάζεις would be; the head noun doesn’t change its case to match the relative clause.

Do I need to say εσύ with διαβάζεις?

No. Greek is a pro‑drop language: the verb ending in διαβάζεις already shows you (singular). You add εσύ only for emphasis, e.g., Εσύ διαβάζεις (you, specifically, are reading).

Does διαβάζεις mean both you read and you are reading?

Yes. The present tense in Greek covers both simple and progressive meanings. To stress ongoing action, add an adverb like τώρα: που διαβάζεις τώρα.

How is διαβάζεις formed and pronounced?

Verb: διαβάζω (to read). Present active:
- διαβάζω, διαβάζεις, διαβάζει, διαβάζουμε, διαβάζετε, διαβάζουν(ε).
Pronunciation: διαβάζεις = [ðjaˈvazis]. The initial δ is like English voiced th in this.

What is είναι exactly?

It’s the 3rd person form of είμαι (to be). Present:

είμαι, είσαι, είναι, είμαστε, είστε, είναι. Note that είναι is used for both 3rd singular and 3rd plural; context decides which it is. Pronounced [ˈine].

Why is φθηνό in the neuter and with no article?

Agreement: φθηνό agrees with βιβλίο (neuter singular), so it’s neuter nominative singular.
No article: After είναι, adjectives are used predicatively without an article: είναι φθηνό (it is cheap). Attributively you’d say το φθηνό βιβλίο (the cheap book).

Is there a difference between φθηνό and φτηνό?

Both are accepted. φθηνός/φθηνό is more conservative/standard spelling; φτηνός/φτηνό is very common in everyday writing. Pronunciation differs slightly: φθηνό [fθiˈno] vs φτηνό [ftiˈno].

Should there be a comma before που?

No. This is a restrictive relative clause (it defines which book), so no commas. Non‑restrictive clauses often use ο οποίος and are set off by commas, e.g., το βιβλίο, το οποίο… in more formal style.

Can I move words around for emphasis?

Greek allows some fronting for emphasis. You can say:

Φθηνό είναι το βιβλίο που διαβάζεις (emphasizes cheapness). Keeping που immediately after βιβλίο is natural; don’t separate the noun from its relative clause.

How do I say it in the plural?

Τα βιβλία που διαβάζεις είναι φθηνά.

βιβλία (neuter plural), φθηνά (neuter plural adjective), είναι (same form for plural).

How do I put it in the past?

Ongoing past reading (imperfect): Το βιβλίο που διάβαζες ήταν φθηνό.
Completed past reading (aorist): Το βιβλίο που διάβασες ήταν φθηνό. This mirrors the difference between was in the middle of reading vs finished reading.

Any pronunciation tips for tricky letters here?

β = [v], not English b: βιβλίο = [viˈvlio].
ει = = [ˈine].
ου = = [pu].
δια‑ often sounds like = [ðjaˈvazis].
φθ/φτ clusters: φθηνό [fθiˈno] or φτηνό [ftiˈno].

Can Greek use a pronoun inside the relative clause, like the man that I saw him?

In everyday speech, Greek often uses a resumptive clitic for object relatives, especially with people:

Ο φίλος που τον είδες alongside Ο φίλος που είδες. With neuter objects you might also hear it, e.g., Το βιβλίο που το διαβάζεις, but the safer, more neutral form is Το βιβλίο που διαβάζεις (no clitic).