Learn Hardcore Greek: Δεν μου αρέσει όταν κάποιος καπνίζει τσιγάρο δίπλα μου, ειδικά σε κλειστό χώρο. - I don’t like it when someone smokes a cigarette next to me, especially in a closed space.

In Greek, αρέσει literally means “is pleasing”, so the grammatical subject is the thing that pleases, and the person who likes it is an indirect object:

Μου αρέσει ο καφές. = Coffee pleases me → I like coffee.

So Δεν μου αρέσει = It does not please me → I don’t like it.
Δεν αρέσω would mean I am not liked (by others), which is a different meaning.
Δεν αρέσει σε μένα is grammatically possible but sounds heavier and is used only for emphasis; the normal everyday form is Δεν μου αρέσει with the weak pronoun μου.

Why do we use μου here and not με or εμένα?

μου is the weak (clitic) form used mostly as an indirect object: Μου αρέσει, Μου δίνεις;
με is the weak form used as a direct object: Με βλέπεις; (Do you see me?)
εμένα is the strong/stressed form, used for emphasis: Εμένα δεν μου αρέσει.

With αρέσει we always use the indirect-object type: μου, σου, του, της, μας, σας, τους.
So Δεν μου αρέσει is the natural choice here.

Why is the negative δεν and not μην in this sentence?

Modern Greek has two main negative particles:

δεν is used with indicative verbs (normal statements about reality):
Δεν μου αρέσει, Δεν πάω σχολείο σήμερα.
μην is used mainly with subjunctive / imperative or after some particles like να, ας:
Να μην πας, Μην καπνίζεις.

In Δεν μου αρέσει όταν κάποιος καπνίζει…, both αρέσει and καπνίζει are in the indicative, so δεν is the correct negative.

Why do we say όταν here and not αν? What is the nuance?

όταν means “when/whenever” and is used for time:

Όταν κάποιος καπνίζει δίπλα μου… = When(ever) someone smokes next to me…

αν means “if” and is used for conditions:

Αν κάποιος καπνίσει δίπλα μου… = If someone smokes next to me… (conditional situation).

Here the speaker is talking about a general situation that occurs in time, not a hypothetical condition, so όταν is more natural. It implies whenever this happens in general, I don’t like it.

What exactly does κάποιος mean here, and why is it masculine?

κάποιος means “someone / anybody” in a general, indefinite way. It doesn’t refer to a specific person.

The form κάποιος is grammatically masculine singular, but in practice Greek often uses the masculine as a generic gender when talking about a person of unknown or irrelevant gender.

You could also say:

όταν ένας άνθρωπος καπνίζει… (when a person smokes…)
όταν καπνίζει κάποιος δίπλα μου… (same meaning, different word order)

All are fine; κάποιος is just the most compact, natural “someone” here.

Why do we say καπνίζει τσιγάρο and not just καπνίζει?

Both are possible:

όταν κάποιος καπνίζει = when someone smokes (in general)
όταν κάποιος καπνίζει τσιγάρο = when someone smokes a cigarette

Adding τσιγάρο specifies what is being smoked – a cigarette, not, say, a cigar or something else. In everyday speech, many Greeks would simply say:

Δεν μου αρέσει όταν καπνίζουν δίπλα μου…

and leave out τσιγάρο, because it’s obvious from context. Including τσιγάρο is not wrong; it’s just a bit more explicit.

Can the word order in κάπνίζει τσιγάρο δίπλα μου change? For example, can I say κάπνίζει δίπλα μου τσιγάρο?

Greek word order is fairly flexible, so several versions are grammatical:

κάποιος καπνίζει τσιγάρο δίπλα μου (most neutral)
κάποιος καπνίζει δίπλα μου τσιγάρο
κάποιος δίπλα μου καπνίζει τσιγάρο

The main difference is emphasis and rhythm, not meaning.
The original καπνίζει τσιγάρο δίπλα μου sounds natural and neutral; moving δίπλα μου earlier can put a bit more focus on the place (next to me), but all are understandable.

What is the difference between δίπλα μου and something like κοντά μου or πλάι μου?

All three indicate closeness, but with slightly different nuances:

δίπλα μου = right next to me, usually side by side, very close.
πλάι μου is very similar to δίπλα μου, often a bit more poetic/literary but also used in speech.
κοντά μου = near me, which can be a bit less immediate; the person might not be directly at your side but still in your vicinity.

In the context of smoke, δίπλα μου is ideal because it implies very close, where the smoke really bothers you.

What exactly does σε κλειστό χώρο mean, and why is there no article (τον, έναν)?

σε κλειστό χώρο literally means “in a closed/enclosed space” and is the standard way to say indoors / in an enclosed area (e.g. rooms, offices, cars, etc.).

The noun phrase is κλειστός χώρος (closed space), and here we have it in the accusative singular: κλειστό χώρο after σε.

There is no article because we are talking in a general, non-specific sense: in an enclosed space (as a type of environment), not in a particular enclosed space. Adding an article, e.g. σε έναν κλειστό χώρο, would feel more like in a certain enclosed space.

Is ειδικά here more like “especially” or “particularly”? Could we use ιδιαίτερα instead?

ειδικά in this sentence means “especially / in particular”, focusing on the specific case of a closed space:

…δίπλα μου, ειδικά σε κλειστό χώρο.
…next to me, especially in an enclosed space.

You could also say ιδιαίτερα σε κλειστό χώρο, which is very close in meaning and also natural.
Subtle nuance: ειδικά can sound a bit more sharp/contrastive (this case in particular), while ιδιαίτερα can feel slightly more descriptive/intensifying, but in everyday use they often overlap.

Could I also say Δεν μου αρέσει να καπνίζουν δίπλα μου instead of using όταν κάποιος καπνίζει? Is there any difference?

Yes, both are possible:

Δεν μου αρέσει όταν κάποιος καπνίζει τσιγάρο δίπλα μου…
Δεν μου αρέσει να καπνίζουν δίπλα μου…

The όταν-clause presents it as a situation in time: When someone smokes next to me, I don’t like it.
The να + 3rd person plural (να καπνίζουν) is more impersonal/generic, like saying I don’t like people smoking next to me (in general).

Both are natural; the second is very common in everyday speech, especially without κάποιος:

Δεν μου αρέσει να καπνίζουν δίπλα μου, ειδικά σε κλειστό χώρο.

In speech, I often see δε μ’ αρέσει instead of Δεν μου αρέσει. Is that the same?

Yes, it’s the same phrase in a more colloquial / contracted form:

Δεν μου αρέσει → often pronounced and written as δε μου αρέσει
With elision before a vowel: δε μ’ αρέσει

So:

Δε μου αρέσει όταν κάποιος καπνίζει…
Δε μ’ αρέσει όταν καπνίζουν δίπλα μου…

are just more informal spellings of Δεν μου αρέσει…. The meaning and grammar are identical.