Learn Hardcore Greek: Όταν έχει πολλά αστέρια, νιώθω πιο ήρεμος στο πάρκο. - When there are many stars, I feel calmer in the park.

weather and natural conditions:
- Έχει ήλιο. = There is sun / It’s sunny.
- Έχει σύννεφα. = There are clouds.
general presence of things/people:
- Έχει πολύ κόσμο. = There are many people.

So Όταν έχει πολλά αστέρια is literally "When it has many stars", but idiomatically it means "When there are many stars (in the sky)".

Using έχει like this is very natural and common in spoken Greek.

Where is "there" or "in the sky" in the Greek sentence? Why is it not written?

It’s understood from context and usually left out.

In Greek, Όταν έχει πολλά αστέρια automatically suggests "when there are many stars in the sky".
The location (the sky) is obvious from the type of thing we’re talking about (stars), so it doesn’t need to be mentioned unless you want to be very explicit.

You can say it explicitly:

Όταν έχει πολλά αστέρια στον ουρανό, νιώθω πιο ήρεμος στο πάρκο.
= When there are many stars in the sky, I feel calmer in the park.

But in normal conversation, Όταν έχει πολλά αστέρια is enough.

What tense are έχει and νιώθω? How do I know if it means "I feel" or "I am feeling"?

Both έχει and νιώθω are:

Present tense
Indicative mood
Active voice

In Greek, the same present tense form covers both English "I feel" and "I am feeling":

νιώθω = I feel / I am feeling
έχει = it has / there is / there are (right now / generally)

Context tells you whether the meaning is:

habitual/general:
Όταν έχει πολλά αστέρια, νιώθω πιο ήρεμος.
= Whenever there are many stars, I (generally) feel calmer.
or right now / this time:
Σήμερα που έχει πολλά αστέρια, νιώθω πιο ήρεμος.
= Today, since there are many stars, I am feeling calmer.

Greek does not make a formal distinction like English simple vs continuous (feel / am feeling) in the present.

Why is there a comma after αστέρια in Όταν έχει πολλά αστέρια, νιώθω πιο ήρεμος στο πάρκο?

Because the first part is a subordinate clause introduced by όταν:

Όταν έχει πολλά αστέρια = When there are many stars (time clause)
νιώθω πιο ήρεμος στο πάρκο = I feel calmer in the park (main clause)

In Greek, when a clause introduced by words like όταν, επειδή, αν, ενώ comes first, we usually separate it from the main clause with a comma:

Όταν τελειώσω, θα φύγω.
Επειδή βρέχει, μένω σπίτι.

If the main clause comes first, the comma is often omitted:

Νιώθω πιο ήρεμος στο πάρκο όταν έχει πολλά αστέρια.

Why is there no word for "I" before νιώθω? Shouldn’t it be εγώ νιώθω?

Greek is a "pro-drop" language: subject pronouns are usually omitted because the verb ending already tells you the person:

νιώθω = I feel
νιώθεις = you feel
νιώθει = he/she/it feels

So νιώθω alone already means "I feel".

You only add εγώ when you want to:

put emphasis on the subject:
- Εγώ νιώθω πιο ήρεμος, όχι εσύ. = I feel calmer, not you.
or contrast different subjects.

In a neutral sentence like this one, εγώ is normally left out.

Why is it πιο ήρεμος and not πιο ήρεμα? What is the difference?

πιο ήρεμος is an adjective (masculine, singular, nominative)
πιο ήρεμα is an adverb

In this sentence, we are describing the state of the person (the subject "I"), so we need an adjective:

νιώθω πιο ήρεμος = I feel calmer / more calm (I, as a person, am calmer)

If you say:

νιώθω πιο ήρεμα
that focuses more on how you are feeling/behaving, like "I feel in a more calm way / more calmly", often describing manner rather than inner state.

In practice, both can appear in similar contexts, but:

νιώθω πιο ήρεμος = state of being (I am calmer)
μιλάω πιο ήρεμα = manner (I speak more calmly)

Here, describing your internal calmness, πιο ήρεμος is the natural choice.

How would the sentence change if the speaker is female or if we are talking about more than one person?

The verb νιώθω stays the same, but the adjective ήρεμος must agree in gender and number with the subject.

Female speaker (singular)
- Όταν έχει πολλά αστέρια, νιώθω πιο ήρεμη στο πάρκο.
  (ήρεμη = feminine singular)
Group of males or mixed group (we)
- Όταν έχει πολλά αστέρια, νιώθουμε πιο ήρεμοι στο πάρκο.
  (ήρεμοι = masculine plural)
Group of only females (we)
- Όταν έχει πολλά αστέρια, νιώθουμε πιο ήρεμες στο πάρκο.
  (ήρεμες = feminine plural)

Adjectives in Greek always agree with the noun or pronoun they describe.

What exactly is στο in στο πάρκο? Why not just σε?

στο is a contraction:

σε (in, at, to) + το (the, neuter singular) → στο

So:

σε το πάρκο → στο πάρκο = in/at the park

This is very regular in Greek:

σε + τον → στον
- στον δρόμο (in/on the road)
σε + την → στη(ν)
- στη στάση (at the stop)
σε + τους → στους
- στους φίλους μου (to my friends)

You would use bare σε only without a definite article, e.g.:

πάω σε πάρκο = I go to a park (less specific, also less common; Greeks often still use the article).

Why is there no article before πολλά αστέρια but there is το before πάρκο?

Two different ideas:

πολλά αστέρια = many stars (indefinite quantity)
- We’re talking about some/many stars, not a specific known group.
- In Greek, vague quantities with words like πολλά, λίγα, αρκετά, πολύ often do not take the article:
  - πολλά παιδιά = many children
  - λίγα χρήματα = little money
στο πάρκο = in the park
- Here, το πάρκο is definite: “the park” (probably the one we usually go to / know about).
- Greek uses the definite article more often than English, especially with places:
  - στο σχολείο = at school
  - στο σπίτι = at home
  - στο γραφείο = at the office

So: no article before a general quantity, but article before a concrete, known place.

Why is αστέρια in that form? What gender and case is it, and why?

αστέρια is:

neuter
plural
accusative

The basic noun is:

το αστέρι = the star (singular, neuter)
τα αστέρια = the stars (plural, neuter nominative/accusative)

In the sentence:

έχει is a transitive verb ("has")
πολλά αστέρια is its direct object → so it must be in the accusative case.

Structure:

(it) has what? → πολλά αστέρια (accusative plural)

Note: Neuter plural forms in -ια are often the same in nominative and accusative (e.g. τα παιδιά, τα βιβλία, τα αστέρια), so the case here is decided by the role in the sentence.

Could I say Όταν είναι πολλά αστέρια instead of Όταν έχει πολλά αστέρια?

You could say Όταν είναι πολλά αστέρια στον ουρανό, but:

Όταν έχει πολλά αστέρια is much more natural and idiomatic for “When there are many stars (in the sky)”.
είναι tends to sound more like:
- Όταν ο ουρανός είναι γεμάτος αστέρια = When the sky is full of stars
  or
- Όταν τα αστέρια είναι πολλά = When the stars are many

So:

Όταν έχει πολλά αστέρια = the standard everyday way to say “when there are many stars”.
Όταν είναι πολλά αστέρια on its own sounds awkward; it wants something like στον ουρανό or a different structure.

What is the difference between νιώθω and αισθάνομαι? Could I use αισθάνομαι here?

Both verbs can mean "to feel", and in this sentence they are basically interchangeable:

Όταν έχει πολλά αστέρια, νιώθω πιο ήρεμος στο πάρκο.
Όταν έχει πολλά αστέρια, αισθάνομαι πιο ήρεμος στο πάρκο.

Differences in usage:

νιώθω
- more colloquial, very frequent in everyday speech
- can be used for both physical and emotional feeling:
  - νιώθω κρύο = I feel cold
  - νιώθω χαρά = I feel joy
αισθάνομαι
- often sounds a bit more formal / literary, though still common
- also used for feelings and sensations:
  - αισθάνομαι κουρασμένος = I feel tired

In your sentence, νιώθω is slightly more natural in casual speech, but αισθάνομαι is also correct.

Could I use άμα instead of όταν? What is the difference?

Yes, you can say:

Άμα έχει πολλά αστέρια, νιώθω πιο ήρεμος στο πάρκο.

Differences:

όταν = when (neutral, standard; used in both written and spoken Greek)
άμα = when / if (more colloquial, very common in spoken Greek)

In many everyday contexts, άμα and όταν overlap:

Όταν πας σπίτι, πάρε με τηλέφωνο.
Άμα πας σπίτι, πάρε με τηλέφωνο.

For learners, όταν is the safer, more standard choice in writing, but you will hear άμα all the time in speech.

Is the word order flexible? Can I move Όταν έχει πολλά αστέρια to the end?

Yes, Greek word order is relatively flexible. You can say:

Νιώθω πιο ήρεμος στο πάρκο όταν έχει πολλά αστέρια.

Both versions are correct:

Όταν έχει πολλά αστέρια, νιώθω πιο ήρεμος στο πάρκο.
Νιώθω πιο ήρεμος στο πάρκο όταν έχει πολλά αστέρια.

Differences are mostly about emphasis and rhythm:

Starting with Όταν έχει πολλά αστέρια puts more focus on the condition / time.
Starting with Νιώθω πιο ήρεμος στο πάρκο starts with how you feel, then explains when.

Grammatically, both are fine.

Can I use this structure with other nouns, like “When there are many people in the park, I feel calmer”?

Yes, the pattern Όταν έχει + [amount] + [noun] is very productive:

Όταν έχει πολύ κόσμο στο πάρκο, νιώθω πιο ήρεμος.
= When there are a lot of people in the park, I feel calmer.
Όταν έχει λίγη κίνηση, οδηγώ πιο γρήγορα.
= When there is little traffic, I drive faster.
Όταν έχει θόρυβο, δεν συγκεντρώνομαι.
= When there is noise, I can’t concentrate.

So you can reuse:

Όταν έχει [πολύ / λίγο / αρκετό] + [noun] ...
to express "When there is/are..." in many situations.