Learn Hardcore Greek: Η δασκάλα μας λέει ότι είναι καλό να διαβάζουμε και κλασικά βιβλία, όχι μόνο σύγχρονα. - Our teacher tells us that it is good to read classic books too, not only modern ones.

In this sentence, though, μας clearly belongs to η δασκάλα (our teacher), not to λέει (tells us), because of the word order and natural reading:
Η δασκάλα μας λέει… = Our teacher tells (us) that…

Why is there no subject pronoun like αυτή (she)? How do we know who is speaking?

Greek normally omits subject pronouns because the subject is clear from:

The verb ending, and/or
A stated noun

Here, the subject is already given by the noun phrase Η δασκάλα μας. That’s enough; saying Αυτή, η δασκάλα μας, λέει… would be grammatically possible but unnecessary and slightly heavy in normal speech.

So:

Η δασκάλα μας λέει… = Our teacher says/tells (us)…
(no need for αυτή).

What does λέει ότι mean, and is ότι the same as ό,τι?

λέει ότι means says that / tells (us) that.

λέει = he/she says / tells
ότι = that (conjunction introducing a subordinate clause)

Example:

Μου είπε ότι θα έρθει. = He told me that he will come.

This ότι is not the same as ό,τι.

ότι (no comma) = that (conjunction)
ό,τι (with comma) = whatever / anything that (relative pronoun)

Examples:

Ξέρω ότι έχεις δίκιο. = I know that you’re right.
Πάρε ό,τι θέλεις. = Take whatever you want.

Why do we say είναι καλό να διαβάζουμε and not something like είναι καλό διαβάζουμε?

Greek generally needs να to introduce a clause with a verb that functions like an infinitive in English.

είναι καλό να διαβάζουμε = it is good to read / for us to read

There is no separate infinitive form in Modern Greek. Instead, you:

Use να
Put the verb in a finite form (here: present, 1st person plural)

So you cannot say είναι καλό διαβάζουμε; you need να:

είναι καλό να διαβάζουμε
είναι σημαντικό να μιλάς ελληνικά = it’s important to speak Greek

Is διαβάζουμε here present tense or subjunctive?

Formally, διαβάζουμε is the present tense, 1st person plural. Greek doesn’t have a separate “subjunctive form” for most verbs; instead, the same form is used and the mood is indicated by the particle να.

So:

διαβάζουμε on its own = we read / we are reading
να διαβάζουμε = (that) we read / (for) us to read

Because it is introduced by να, we call it a subjunctive use of the present (υποτακτική ενεστώτα), even though the form looks identical to the indicative.

Why is να διαβάζουμε used instead of να διαβάσουμε?

Greek distinguishes between:

Present subjunctive (να διαβάζουμε) = ongoing, repeated, or habitual action
Aorist subjunctive (να διαβάσουμε) = single, complete action

In this sentence, the teacher is talking about reading in general, as a habitual / regular activity:

είναι καλό να διαβάζουμε και κλασικά βιβλία
= it is good for us to (generally) read classical books too

If you said να διαβάσουμε, it would suggest a more specific, one-time action (for us to read [them, once]), which doesn’t fit the general advice here.

What is the role of και in να διαβάζουμε και κλασικά βιβλία?

Here και means also / too, not just and.

να διαβάζουμε κλασικά βιβλία = to read classical books
να διαβάζουμε και κλασικά βιβλία = to also read classical books / to read classical books too

So the idea is:

not only modern books, but classical ones too.

This και is often paired with όχι μόνο later in the sentence:

να διαβάζουμε και κλασικά βιβλία, όχι μόνο σύγχρονα
= to read classical books too, not only modern ones

Why is there no article before κλασικά βιβλία? Why not τα κλασικά βιβλία?

Greek can omit the article when talking about things in general, especially with plural countable nouns:

κλασικά βιβλία = classical books (in general)
σύγχρονα βιβλία = modern books (in general)

If you said τα κλασικά βιβλία, it would sound more like the classical books (a more specific set of books), which is not what is meant here. The teacher is talking about types of books in general, so no article is natural:

Μου αρέσουν τα κλασικά βιβλία. = I like the classical books.
Μου αρέσουν κλασικά βιβλία. = I like classical books (as a category).

Why is κλασικά in the neuter plural form?

Because it agrees with βιβλία, which is neuter plural.

το βιβλίο (neuter singular) → τα βιβλία (neuter plural)
κλασικό βιβλίο (classical book) → κλασικά βιβλία (classical books)

Adjectives in Greek agree with the noun in:

Gender (masculine, feminine, neuter)
Number (singular, plural)
Case (here: nominative/accusative)

So:

κλασικά βιβλία = classical books
σύγχρονα βιβλία = modern books

In όχι μόνο σύγχρονα, where did the word βιβλία go? What does σύγχρονα stand for?

σύγχρονα here is short for:

σύγχρονα βιβλία = modern books

Greek often drops the noun when it is obvious from context and leaves just the adjective, which behaves like “one(s)” in English:

Μου αρέσουν τα κόκκινα (αυτοκίνητα), όχι τα μπλε.
= I like the red (ones), not the blue (ones).

So:

όχι μόνο σύγχρονα (βιβλία)
= not only modern (ones / books)

Why is there a comma before όχι μόνο?

The comma marks a contrastive phrase that adds an extra comment:

… να διαβάζουμε και κλασικά βιβλία, όχι μόνο σύγχρονα.

It’s similar to English commas in:

… to read classical books, not only modern ones.

You could theoretically omit the comma in very informal writing, but standard punctuation puts it there because όχι μόνο σύγχρονα is an additional, contrasting remark to what came just before.

What is the difference between σύγχρονα and μοντέρνα?

Both can often be translated as modern, but there is a nuance:

σύγχρονα (from σύγχρονος)
- Literally: “of the same time”
- Commonly: contemporary, belonging to the present era, recent
μοντέρνα (from “modern”)
- More “fashionable, trendy, in modern style”

In the context of books, both can work:

σύγχρονα βιβλία = contemporary / modern-era books
μοντέρνα βιβλία = books in a modern style / modern-themed books

Here σύγχρονα suggests “books from our time, recent literature,” which fits well with the contrast to κλασικά βιβλία (classical books).