Learn Hardcore Greek: Πριν να κατέβω στο υπόγειο, βάζω μπουφάν γιατί κρυώνω εκεί κάτω. - Before I go down to the basement, I put on a jacket because I am cold down there.

Since all three verbs clearly show “I” in their endings, Greek doesn’t need to say εγώ unless it wants to emphasize I (as opposed to someone else).

Why is it πριν να κατέβω and not just πριν κατέβω? Is να necessary?

Both forms exist in modern Greek:

πριν να κατέβω στο υπόγειο
πριν κατέβω στο υπόγειο

In everyday speech, πριν να + subjunctive is very common, especially in many dialects and in informal language. In more formal or prescriptive grammar, you’ll often see the recommendation:

Use πριν
- inflected verb (subjunctive) without να:
  πριν κατέβω, πριν φύγουμε, πριν πάει σπίτι.

So:

Your sentence with πριν να κατέβω is perfectly natural in spoken Greek.
If you’re aiming for textbook/standard style, you can drop να and say πριν κατέβω.

Meaning-wise, in this sentence there is no difference in everyday use.

Why is it κατέβω and not κατεβαίνω after πριν?

This is about aspect, not about time.

κατέβω is the aorist subjunctive (focus on the whole, single event: go down, get down once).
κατεβαίνω is the present (imperfective) subjunctive (focus on the process, repeated or ongoing: be going down, keep going down).

After πριν, Greek usually prefers the aorist subjunctive when you’re talking about a single, complete event that must happen before something else:

πριν (να) φάω – before I eat (once)
πριν (να) φύγουμε – before we leave

So πριν (να) κατέβω στο υπόγειο = before I go down to the basement (as a single step), I put on a jacket…

Using πριν (να) κατεβαίνω would sound strange here, because it would make the “going down” sound like a continuous or habitual process in a way that doesn’t fit the structure of this sentence.

Why is βάζω in the present tense, not future like θα βάλω?

In Greek, present tense can express:

habitual / repeated actions
– things you usually do
general truths

Here, βάζω μπουφάν means:

I (normally) put on a jacket
/ Each time before I go down, I put on a jacket.

If you said:

Πριν να κατέβω στο υπόγειο, θα βάλω μπουφάν.

it would sound more like you’re talking about one specific future occasion:

Before I go down to the basement (this time), I will put on a jacket.

So:

βάζω here = habitual, “that’s my usual routine”.
θα βάλω would be a specific future plan.

Why say βάζω μπουφάν and not φοράω μπουφάν? What’s the difference?

Both verbs are used with clothes, but the nuance is different:

βάζω μπουφάν
- literally: I put a jacket (on).
- focuses on the action of putting it on.
- close to English “put on a jacket”.
φοράω μπουφάν
- literally: I wear a jacket.
- focuses on the state of wearing it, or sometimes also on putting it on.

So in your sentence:

βάζω μπουφάν is very natural, because we’re talking about what you do before you go down: you put on a jacket.

You could also hear:

Πριν να κατέβω στο υπόγειο, φοράω μπουφάν…

but βάζω is more directly “put on (now, each time)” and matches the idea of a repeated action.

Why is there no article in βάζω μπουφάν? Why not βάζω ένα μπουφάν or βάζω το μπουφάν?

Greek often omits the article with:

clothes,
food,
professions,
and some other nouns,

when speaking generally or habitually, especially with verbs like βάζω, φοράω, τρώω, πίνω.

Here:

βάζω μπουφάν = I put on a jacket (in general, no specific one implied).

If you said:

βάζω ένα μπουφάν – also possible, a bit more like “I put on a jacket (one jacket)”
βάζω το μπουφάν – “I put on the jacket” (a specific one, known from context, e.g. my usual jacket)
βάζω το μπουφάν μου – “I put on my jacket”.

In your sentence, the speaker just means “I put on a jacket” as a general habit, so the article is naturally dropped.

What exactly does στο υπόγειο mean, and how is στο formed?

στο υπόγειο means “to the basement / in the basement”, depending on context.

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

They combine into:

σε + το → στο

So:

στο υπόγειο = in/to the basement.

Greek often uses σε + article like this:

στο σπίτι – at home / to the house
στο σχολείο – at school / to school
στο γραφείο – at the office / to the office

The exact English preposition (in / at / to) depends on context; Greek uses σε for all of them.

Why do we have both εκεί and κάτω in εκεί κάτω? Isn’t one of them enough?

εκεί κάτω literally means “down there”, combining:

εκεί = there
κάτω = down / below

If you only said εκεί, it would just mean “there” (no vertical sense).
If you only said κάτω, it would mean “downstairs / below / down”, but not clearly contrasted with “here”.

εκεί κάτω:

emphasises that the place is downward and not here,
corresponds very well to English “down there”.

So:

κρυώνω εκεί κάτω = I’m cold down there (in that lower place, the basement), not up here.

What does κρυώνω mean exactly? Is it “I am cold” or “it’s cold”?

κρυώνω = I feel cold / I am cold (verb, 1st person singular).

It describes the person’s sensation, not the weather itself.

Compare:

κρυώνω – I’m cold (I feel cold).
κρυώνεις; – Are you cold?
κάνει κρύο – It’s cold (the weather is cold).
είναι κρύο το υπόγειο – The basement is cold.
είμαι κρυωμένος – I have a cold (I’m sick / I’m chilled).

So in γιατί κρυώνω εκεί κάτω, the meaning is:

because I feel cold down there (when I’m in the basement).

Can the word order change? For example, can I say Βάζω μπουφάν πριν να κατέβω στο υπόγειο, γιατί κρυώνω εκεί κάτω?

Yes. Greek word order is fairly flexible, especially for clauses like πριν να… and γιατί….

These are all grammatical and natural (with slightly different emphasis):

Πριν (να) κατέβω στο υπόγειο, βάζω μπουφάν γιατί κρυώνω εκεί κάτω.
Βάζω μπουφάν πριν (να) κατέβω στο υπόγειο, γιατί κρυώνω εκεί κάτω.
Βάζω μπουφάν, γιατί κρυώνω εκεί κάτω, πριν (να) κατέβω στο υπόγειο.
(less common, but possible in the right context)

Putting πριν (να) κατέβω… at the beginning highlights the time condition (“before I go down…”).
Putting βάζω μπουφάν first focuses more on the action (“I put on a jacket before I go down…”).

Why is γιατί used here? Could we also use επειδή?

Both γιατί and επειδή can mean “because”, but:

γιατί is more common in everyday speech.
επειδή is a little more neutral or slightly more formal, but still very common.

In your sentence:

βάζω μπουφάν γιατί κρυώνω εκεί κάτω.
βάζω μπουφάν επειδή κρυώνω εκεί κάτω.

Both are fine and mean “I put on a jacket because I’m cold down there.”

So yes, you could replace γιατί with επειδή here without changing the meaning.