Learn Hardcore Greek: Ο αέρας σήμερα είναι πολύ κρύος, οπότε μένω σπίτι. - The air today is very cold, so I stay at home.

Ο αέρας
- We’re talking about a specific, identifiable air (the air today, outside now), so Greek normally uses the definite article:
  - ο αέρας = the air
- Greek uses the definite article more often than English in such cases.
σπίτι
- Here σπίτι is used in a fixed, almost adverbial way to mean (at) home in general, not the house as a specific building.
- Compare:
  - μένω σπίτι = I stay (at) home.
  - μένω στο σπίτι = I stay in the (particular) house / at the house.

So: specific physical thing → article (ο αέρας); idiomatic “home” meaning → usually no article (σπίτι).

Is ο αέρας the same as saying the weather in Greek?

Not exactly.

ο αέρας = the air, the air itself (what you feel on your skin, what you breathe).
ο καιρός = the weather.

In this sentence:

Ο αέρας σήμερα είναι πολύ κρύος focuses on the coldness of the air itself.
If you wanted to talk more generally about the weather, you’d say:
- Ο καιρός σήμερα είναι πολύ κρύος. = The weather today is very cold.

Both are possible in real life, but they are not identical in meaning.

Why is σήμερα placed after ο αέρας? Can I say Σήμερα ο αέρας είναι πολύ κρύος?

Yes, you can absolutely say:

Σήμερα ο αέρας είναι πολύ κρύος, οπότε μένω σπίτι.

Word order is more flexible in Greek than in English. Differences:

Ο αέρας σήμερα είναι πολύ κρύος
- Slightly more neutral, with light emphasis on o αέρας (the air today, as opposed to yesterday or in general).
Σήμερα ο αέρας είναι πολύ κρύος
- Puts a little extra focus on σήμερα (today), like “Today, the air is very cold.”

Both are perfectly natural; it’s mostly about subtle emphasis, not grammar.

Why do we use είναι and μένω (present tense) even though this is about “today”? In English we might say “is being” or “I’m staying”.

Greek has one present tense form that covers both:

simple present: I stay
present continuous: I am staying

So:

είναι = is / is being (context decides)
μένω = I stay / I am staying

In this sentence:

Ο αέρας σήμερα είναι πολύ κρύος
οπότε μένω σπίτι

both naturally mean something like:

The air is very cold today, so I’m staying home.

Greek does not need a separate continuous form here; the simple present covers it.

Why do we say πολύ κρύος and not something like πολύς κρύος or πολύ κρύο?

Two points:

πολύ as an adverb:
- Here πολύ modifies the adjective κρύος (cold) and means very.
- As an adverb, πολύ is invariable; it does not change for gender, number, or case:
  - πολύ κρύος (very cold – masc.)
  - πολύ κρύα (very cold – fem.)
  - πολύ κρύο (very cold – neut.)
πολύς as an adjective (different word):
- πολύς / πολλή / πολύ = much / many / a lot of when used as an adjective before a noun:
  - πολύς αέρας = a lot of air
  - πολλή βροχή = a lot of rain

In our sentence πολύ is not “much”, it is the adverb very modifying κρύος, so it stays πολύ and does not agree in gender.

Why is the adjective κρύος masculine? Could I use κρύο instead?

κρύος agrees with ο αέρας, which is masculine:

ο αέρας → masculine singular, nominative
The adjective must also be masculine singular nominative: κρύος

So:

ο αέρας είναι κρύος = the air is cold.

You can see πολύ κρύο in Greek, but that’s neuter and usually used:

As a neuter noun:
- Έχει πολύ κρύο. = It’s very cold. (literally: it has much cold)
As a neuter adjective with a neuter noun:
- Το νερό είναι πολύ κρύο. = The water is very cold.

In your sentence the adjective is describing ο αέρας, so it must be κρύος.

What exactly does οπότε mean, and how is it different from γι’ αυτό or άρα?

οπότε is a conjunction meaning roughly so / therefore / and so. It introduces a result or consequence.

Ο αέρας σήμερα είναι πολύ κρύος, οπότε μένω σπίτι.
→ The air is very cold today, so I’m staying home.

Comparison:

γι’ αυτό (from για αυτό) = for this (reason), that’s why
- Slightly more explicit cause-effect:
  - Ο αέρας σήμερα είναι πολύ κρύος· γι’ αυτό μένω σπίτι.
άρα = thus / therefore
- Often a bit more formal or logical in tone:
  - Ο αέρας σήμερα είναι πολύ κρύος, άρα μένω σπίτι.
οπότε is very common in speech, a bit conversational, and often feels like “and so / so then”.

All three can be used here; choice is mostly about style and tone, not grammar.

Why is there a comma before οπότε?

The sentence has two clauses:

Ο αέρας σήμερα είναι πολύ κρύος
οπότε μένω σπίτι

οπότε links them with a cause–result relationship. In Greek, when a linking conjunction connects two independent (or almost independent) clauses, we usually separate them with a comma:

[Clause 1], οπότε [Clause 2].

You could also see a semicolon (·) before other connectors like γι’ αυτό, but the comma before οπότε is normal and standard.

Why do we say μένω σπίτι and not μένω στο σπίτι? What’s the difference?

Both forms are correct but not identical in nuance.

μένω σπίτι
- Idiomatic expression meaning I stay (at) home in general.
- Focus is on the activity of staying home rather than on a specific house as a physical location.
- Very common in everyday speech.
μένω στο σπίτι
- Literally: I stay in the house / at the house.
- You might use this if you’re emphasizing that you’re staying inside the house instead of going out, or you’re referring to a particular house that’s already known from context.

In your sentence, μένω σπίτι nicely matches English “I’m staying home” as a general plan for today.

Could I say θα μείνω σπίτι instead of μένω σπίτι? How would that change the meaning?

Yes:

Ο αέρας σήμερα είναι πολύ κρύος, οπότε θα μείνω σπίτι.

This uses the future tense θα μείνω = I will stay.

Nuance:

μένω σπίτι here often implies a present/near-future plan already adopted:
- “so I (am) stay(ing) home” – a decision that feels current.
θα μείνω σπίτι sounds a bit more like an explicit, perhaps just-made decision about the future:
- “so I will stay home.”

Both are natural; the original with μένω is very conversational and immediate.

Why is there no εγώ (I) before μένω? How do we know who is staying home?

Greek is a “pro-drop” language: subject pronouns are often omitted because the verb ending already tells you the person.

μένω ends in -ω, which is the typical 1st person singular present ending: I stay / I am staying.
So μένω σπίτι by itself clearly means I stay home.

You can include εγώ for emphasis:

… οπότε εγώ μένω σπίτι.
→ “…so I am staying home.” (contrastive emphasis: not someone else)

But the default, neutral form drops εγώ.

How is αέρας pronounced, and why is the accent on αέ instead of the last syllable?

Pronunciation:

αέρας is pronounced approximately a-É-ras:
- α = a (as in “father”)
- ε = e (as in “met”)
- ρ = rolled or tapped r
- ς = s

The written sequence αι here is not the digraph αι pronounced “e” (as in ένα). Because of the accent, α and ε belong to different syllables:

α-έ-ρας (three syllables)

The accent is on the middle syllable -έ-. Greek words typically have one written accent on the stressed syllable; here it shows where the stress falls: α–Έ–ρας.

Are there some natural alternative ways to say this sentence in Greek?

Yes, a few very natural variants:

Σήμερα ο αέρας είναι πολύ κρύος, οπότε μένω σπίτι.
– Moves σήμερα to the front for emphasis on “today”.
Ο καιρός σήμερα είναι πολύ κρύος, γι’ αυτό μένω σπίτι.
– Uses ο καιρός (the weather) and γι’ αυτό instead of οπότε.
Έχει πολύ κρύο σήμερα, γι’ αυτό μένω σπίτι.
– Literally: “It has much cold today, that’s why I’m staying home.”
– Very idiomatic way to say “It’s very cold today, so I’m staying home.”

All convey essentially the same idea with slightly different focus or style.