Learn Hardcore Greek: Νομίζω ότι αυτή ερωτεύεται εύκολα όταν κάποιος είναι ευγενικός. - I think that she falls in love easily when someone is polite.

You can often omit ότι in speech:
Νομίζω αυτή ερωτεύεται εύκολα… – understandable, and colloquial.
You can replace ότι with πως:
Νομίζω πως αυτή ερωτεύεται εύκολα… – very common and natural.

Ότι and πως are usually interchangeable after verbs like νομίζω, πιστεύω, λέω.
Keeping ότι/πως often makes the sentence a bit clearer and more natural, especially in writing.

Why is αυτή (she) used? Could I just say Νομίζω ότι ερωτεύεται εύκολα… without it?

In Greek, the subject pronoun is usually dropped when it’s clear from the verb ending:

Ερωτεύεται already tells you the subject is third person singular (he/she/it).

So:

Νομίζω ότι ερωτεύεται εύκολα…
is perfectly correct and sounds neutral: I think (she) falls in love easily…

When you add αυτή, you usually add emphasis or contrast:

Νομίζω ότι αυτή ερωτεύεται εύκολα…
= I think *she (in particular / as opposed to others) falls in love easily…*

So αυτή here is not required for grammar; it is there for focus: “she, specifically.”

What exactly is ερωτεύεται? Why not ερωτεύει?

Ερωτεύεται is:

3rd person singular
present tense
middle/passive voice of ερωτεύομαι (to fall in love)

In modern Greek:

ερωτεύομαι κάποιον = I fall in love with someone
ερωτεύεται = she falls in love (with someone, implied)

If you said ερωτεύει, that would be active voice, meaning something like:

ερωτεύει κάποιον ≈ she makes someone fall in love / she loves someone passionately

This sounds strange or archaic in modern Greek in this meaning.
For the everyday idea “fall in love”, Greek uses the middle form: ερωτεύομαι, e.g.:

Εγώ ερωτεύομαι – I fall in love
Αυτή ερωτεύεται – She falls in love

Does ερωτεύεται here mean “is falling in love right now” or “falls in love (in general)”?

Here it expresses a general/habitual action, not a single moment:

ερωτεύεται εύκολα
= she falls in love easily / she tends to fall in love easily

Modern Greek present tense often covers both:

right now (progressive) and
habitual/typical behavior

Context decides which one it is. Because of εύκολα and όταν κάποιος είναι ευγενικός, we’re clearly talking about her general tendency.

Why is the adverb εύκολα placed after ερωτεύεται? Could it go somewhere else?

Ερωτεύεται εύκολα is the most natural word order:

verb + adverb: ερωτεύεται εύκολα = falls in love easily

Other possible positions:

Νομίζω ότι αυτή εύκολα ερωτεύεται όταν… – also possible; the εύκολα sounds a bit more emphatic.
Νομίζω ότι αυτή ερωτεύεται όταν κάποιος είναι ευγενικός εύκολα – this is awkward and unnatural.

In general:

Place adverbs like εύκολα, συχνά, πάντα right after the verb or before it for emphasis, but avoid pushing them too far away from the verb.

Why do we use όταν and not αν here?

Όταν = when / whenever (time)
Αν = if (condition)

In your sentence:

όταν κάποιος είναι ευγενικός
= when/whenever somebody is kind/polite

This describes what usually happens whenever that situation occurs (someone is kind → she falls in love easily).

If you used αν:

…αν κάποιος είναι ευγενικός
= if someone is kind…

That suggests a more hypothetical condition: “if it happens that someone is kind, then…” It could work in some contexts, but όταν here sounds more natural for her typical reaction whenever that happens.

Why is it κάποιος and not κάποιον?

Κάποιος here is the subject of the verb είναι:

κάποιος είναι ευγενικός
= someone is kind/polite

Subjects of είμαι (to be) take the nominative case:

κάποιος (nom.) – someone
κάποιον (acc.) – someone (object)

We’d use κάποιον as a direct object, e.g.:

Ερωτεύεται κάποιον. – She falls in love with someone.

But in your sentence, κάποιος is not an object; it is the one who is kind (subject), so nominative is correct: κάποιος είναι ευγενικός.

Can I change the word order inside όταν κάποιος είναι ευγενικός?

Yes, Greek word order is flexible. Common options:

όταν κάποιος είναι ευγενικός – neutral, standard.
όταν είναι κάποιος ευγενικός – also possible, a slightly different rhythm.
όταν κάποιος ευγενικός είναι – grammatically possible, but sounds unusual/poetic.

The most natural everyday form is exactly what you have:

όταν κάποιος είναι ευγενικός

What is the nuance of ευγενικός? Does it mean “kind” or “polite”?

Ευγενικός can mean:

polite / well-mannered (follows social rules, says “please/thank you”)
kind / considerate (treats you gently and respectfully)

Context decides which meaning is stronger. In this sentence, it usually suggests a mix of:

He is polite, attentive, considerate, the sort of behavior that can make her fall in love.

If you wanted to stress “good / nice” in a broader moral sense, you might use:

καλός – good, nice (character, heart)
τρυφερός – tender
στοργικός – affectionate

But ευγενικός focuses more on polite, respectful, gentle behavior.

Could I say Νομίζω πως αυτή ερωτεύεται εύκολα όταν κάποιος είναι ευγενικός instead? Is there any difference?

Yes, you can. The alternatives:

Νομίζω ότι αυτή ερωτεύεται εύκολα…
Νομίζω πως αυτή ερωτεύεται εύκολα…

are both correct and very common. In everyday modern Greek:

ότι and πως after verbs like νομίζω, πιστεύω, λέω are practically interchangeable.
Some speakers feel πως is a bit more colloquial or “softer,” but the difference is small.

So your version with πως is perfectly fine.

Could I say Πιστεύω instead of Νομίζω? Is there a difference?

You can say:

Πιστεύω ότι αυτή ερωτεύεται εύκολα όταν κάποιος είναι ευγενικός.

Both νομίζω and πιστεύω can translate as “I think”, but:

Νομίζω – more like I suppose / it seems to me / my impression is…
Πιστεύω – more like I believe / I’m convinced that…

So πιστεύω sounds a bit stronger, expressing a firmer opinion, but grammatically it works in exactly the same way.