Learn Hardcore Greek: Δεν καταλαβαίνω το ωράριο, είναι λίγο περίεργο, δηλαδή δεν ξέρω πότε τελειώνει κάθε μάθημα. - I don’t understand the schedule, it is a bit strange, that is, I don’t know when each class finishes.

ωράριο καταστήματος = opening hours of a shop
ωράριο εργασίας = working hours
ωράριο μαθημάτων = timetable of lessons (which hour each lesson starts/ends)

In your sentence it means the class schedule / timetable, especially the hours each class ends.

Πρόγραμμα is more general: program, timetable, plan (TV program, daily schedule, event program). For school you might also hear:

ωρολόγιο πρόγραμμα = timetable (literally "hourly program")
πρόγραμμα μαθημάτων = course schedule

So ωράριο focuses on the hours, while πρόγραμμα is the whole plan or list of activities.

Why do we say το ωράριο with the article? In English I might just say “I don’t understand the schedule”, without “the”.

In Greek, nouns very often take a definite article (ο, η, το) where English might drop it.

Here, το ωράριο means the specific schedule we’re talking about (for this school, these lessons). Without the article, δεν καταλαβαίνω ωράριο would sound strange or very abstract, like “I don’t understand schedules (as a concept)”.

So:

Δεν καταλαβαίνω το ωράριο. = I don’t understand this schedule (the one we’re dealing with now).
Using το is the natural, normal choice.

Why is there no “I” written in Δεν καταλαβαίνω? How do we know it means “I don’t understand”?

Greek is a “pro‑drop” language: you usually omit subject pronouns (εγώ, εσύ, αυτός…) because the verb ending already tells you who the subject is.

καταλαβαίνω ends in ‑ω, which is the 1st person singular ending in the present tense → “I understand”.

So:

(Εγώ) δεν καταλαβαίνω. = I don’t understand.

Saying εγώ δεν καταλαβαίνω is not wrong; you use it for emphasis (“I don’t understand”, maybe someone else does). In neutral sentences, you usually drop εγώ.

What does λίγο add in είναι λίγο περίεργο? How is that different from είναι περίεργο?

Λίγο means a little / a bit / slightly. Before an adjective, it usually softens your opinion:

είναι περίεργο = it is strange/weird (quite direct)
είναι λίγο περίεργο = it’s a bit / kind of / slightly strange (more polite, less strong)

So the speaker is not saying the schedule is very strange, just that it’s somewhat odd or not very clear. It makes the criticism milder and more conversational.

Why is it περίεργο and not περίεργος or περίεργη?

Adjectives in Greek must agree with the noun they describe in:

gender (masculine / feminine / neuter)
number (singular / plural)
case

The noun ωράριο is:

gender: neuter
number: singular
case: nominative (subject of είναι)

So the adjective must also be neuter singular nominative:

το ωράριο είναι περίεργο

Forms:

περίεργος = masculine (e.g. ο άνθρωπος είναι περίεργος)
περίεργη = feminine (e.g. η γυναίκα είναι περίεργη)
περίεργο = neuter (e.g. το ωράριο είναι περίεργο)

What does δηλαδή mean here, and how is it used in sentences?

Δηλαδή literally means “that is / that means”, and in everyday speech it works like:

“I mean”
“in other words”
“that is to say”

In your sentence:

…είναι λίγο περίεργο, δηλαδή δεν ξέρω πότε τελειώνει κάθε μάθημα.

The second part explains or clarifies the first part. You can understand it as:

“It’s a bit strange, I mean I don’t know when each class ends.”

You can also move δηλαδή around in the clause for style or emphasis:

Δηλαδή, δεν ξέρω πότε τελειώνει κάθε μάθημα.
Δεν ξέρω, δηλαδή, πότε τελειώνει κάθε μάθημα.

All are possible; in speech, δηλαδή is a very common “linking” or filler word.

In δεν ξέρω πότε τελειώνει κάθε μάθημα, why do we use πότε and not όταν for “when”?

Greek distinguishes between:

πότε = when? in questions or indirect questions
όταν = when / whenever in statements/conditions

Here, πότε τελειώνει κάθε μάθημα is an indirect question:

direct: Πότε τελειώνει κάθε μάθημα; = When does each class finish?
indirect: Δεν ξέρω πότε τελειώνει κάθε μάθημα. = I don’t know when each class finishes.

If you used όταν, it would sound like a normal “when” clause, not a question:

Όταν τελειώνει κάθε μάθημα, φεύγω.
= When each lesson ends, I leave.

So with δεν ξέρω, θυμάμαι, θα σου πω, etc., you use πότε for “when”.

Why is τελειώνει in the present tense? We’re talking about lessons that will end in the future, right?

The Greek present tense also expresses habitual / regular actions, not just actions happening “right now”. Here it refers to the usual ending time of each lesson:

πότε τελειώνει κάθε μάθημα;
≈ At what time does each class (normally) end?

This is like English present simple in “Each class finishes at 3:00.” It’s about general timetable facts, not a one‑time future event.

Greek could also use θα τελειώνει for a repeated future action, but for fixed schedules the plain present τελειώνει is very common and natural.

How does κάθε μάθημα work grammatically? Why not κάθε μαθήματα?

Κάθε (= each / every) in Greek is always followed by a singular noun, never a plural:

κάθε μάθημα = each / every lesson
κάθε μέρα = every day
κάθε παιδί = each child

So:

✅ κάθε μάθημα
❌ κάθε μαθήματα (ungrammatical)

Even though you’re logically talking about many lessons, grammatically κάθε + singular is the correct pattern.

What exactly does μάθημα mean? Is it a “class”, a “lesson”, a “course”…?

Μάθημα can correspond to several English words depending on context:

a single class session / lesson
- Το επόμενο μάθημα αρχίζει στις τρεις.
  = The next class/lesson starts at three.
a subject or course
- Το αγαπημένο μου μάθημα είναι τα ελληνικά.
  = My favorite subject/course is Greek.
a private lesson
- Κάνω μάθημα πιάνου.
  = I take piano lessons.

In your sentence, κάθε μάθημα means each class session / each lesson in the timetable.

Why do we use δεν and not μην in Δεν καταλαβαίνω and δεν ξέρω?

Modern Greek has two main negative particles:

δεν (often written δε(ν))
μην (often written μη(ν))

Very roughly:

Use δεν with indicative verb forms (normal statements about reality):
- Δεν καταλαβαίνω. = I don’t understand.
- Δεν ξέρω. = I don’t know.
Use μην with:
- verbs after να, ας, θα in certain constructions (subjunctive-like)
- negative commands
- some fixed expressions

Examples:

Μην μιλάς! = Don’t talk!
Προσπάθησε να μην αργήσεις. = Try not to be late.

Since καταλαβαίνω and ξέρω here are plain statements in the indicative, δεν is the correct choice.

The whole Greek sentence has several commas. Would it be better to make it into three separate sentences?

You often see long, comma‑linked sentences in transcribed spoken Greek. Written more “carefully”, many speakers would indeed split it:

Δεν καταλαβαίνω το ωράριο. Είναι λίγο περίεργο. Δηλαδή, δεν ξέρω πότε τελειώνει κάθε μάθημα.

This version:

is clearer in writing
matches typical spoken pauses
is slightly more formal / standard

The original with commas is fine as informal, conversational Greek; turning them into full stops just makes it more “textbook‑like” without changing the meaning.