Μου αρέσει το αφρόγαλα στον καπουτσίνο, αλλά η αδερφή μου λέει ότι της φαίνεται πολύ βαρύ.

In Greek, αρέσει works more like is pleasing to than I like.

So:

• Μου αρέσει το αφρόγαλα literally means The milk foam is pleasing to me
• Natural English: I like the milk foam

The word μου means to me, and αρέσει is the 3rd person singular form because the thing being liked is το αφρόγαλα.

This is one of the most common Greek patterns:

• Μου αρέσει ο καφές = I like coffee
• Μου αρέσουν οι καφέδες = I like coffees / coffee drinks

Because the subject of the verb is not I. The subject is το αφρόγαλα.

Greek structure:

• Μου = to me
• αρέσει = pleases
• το αφρόγαλα = the milk foam

So the grammar is:

• το αφρόγαλα αρέσει σε μένα = the milk foam pleases me

Since το αφρόγαλα is singular, the verb is singular: αρέσει.

Compare:

• Μου αρέσει το αφρόγαλα = I like the milk foam
• Μου αρέσουν τα γλυκά = I like sweets

Here μου is the weak form of εμένα / σε μένα meaning to me.

In this sentence:

• Μου αρέσει = I like / literally it is pleasing to me

Greek often uses these short unstressed pronouns before the verb:

• μου = to me / my
• σου = to you / your
• του / της = to him/her / his/her

So μου can mean different things depending on context:

• Μου αρέσει = I like
• η αδερφή μου = my sister

Same form, different function.

Αφρόγαλα means milk foam, the foamy milk you get on drinks like cappuccino.

It is a neuter noun:

• το αφρόγαλα

The word is built from:

• αφρός = foam
• γάλα = milk

So it is basically a compound meaning foam-milk or milk foam.

Because it is neuter singular, other words referring to it will also be neuter singular, such as βαρύ later in the sentence.

στον is a contraction of:

• σε = in / on / to
• τον = the

So:

• σε τον → στον

Here στον καπουτσίνο means in the cappuccino.

This is a very common contraction in Greek:

• στον = σε + τον
• στην = σε + την
• στο = σε + το
• στους = σε + τους

So:

• το αφρόγαλα στον καπουτσίνο = the milk foam in the cappuccino

Η αδερφή μου is the normal way to say my sister in Greek.

Structure:

• η αδερφή = the sister
• μου = my

Greek usually expresses possession like this:

• το βιβλίο μου = my book
• η μητέρα μου = my mother
• η αδερφή μου = my sister

So unlike English, Greek normally keeps the definite article:

• literally the sister my
• natural English my sister

You may sometimes hear different word orders for emphasis in speech, but η αδερφή μου is the standard neutral form.

Yes. Αδερφή is very common in everyday Modern Greek.

You may also see:

• αδελφή

Both mean sister. In general:

• αδερφή is the more common everyday spoken form
• αδελφή can sound a bit more formal or conservative

The same happens with αδερφός / αδελφός for brother.

Ότι here means that.

So:

• η αδερφή μου λέει ότι... = my sister says that...

It introduces a subordinate clause, just like English that:

• Λέει ότι είναι κουρασμένη = She says that she is tired
• Νομίζω ότι έχει δίκιο = I think that he/she is right

In everyday English, that is often omitted, but in Greek ότι is very commonly used.

Της φαίνεται literally means it seems to her.

Breaking it down:

• της = to her
• φαίνεται = seems / appears

So:

• της φαίνεται πολύ βαρύ = it seems too heavy to her

This is another very common Greek pattern:

• Μου φαίνεται καλό = It seems good to me
• Σου φαίνεται δύσκολο; = Does it seem difficult to you?
• Του φαίνεται ακριβό = It seems expensive to him

In this sentence, the understood subject is again το αφρόγαλα.

Because the verb φαίνεται takes an indirect object here: to her.

So Greek uses της:

• της φαίνεται = it seems to her

Compare:

• τη(ν) βλέπω = I see her → direct object
• της μιλάω = I speak to her → indirect object
• της φαίνεται βαρύ = it seems heavy to her → indirect object

So της is the correct pronoun because the meaning is to her, not her as a direct object.

Because βαρύ agrees with το αφρόγαλα, which is neuter singular.

Greek adjectives must agree with the noun they describe in gender, number, and case.

Here:

• το αφρόγαλα = neuter singular
• therefore βαρύ = neuter singular form of heavy

Compare:

• ο καφές είναι βαρύς = the coffee is heavy/strong
• η κρέμα είναι βαριά = the cream is heavy
• το αφρόγαλα είναι βαρύ = the milk foam is heavy

So in της φαίνεται πολύ βαρύ, the adjective matches the understood noun αφρόγαλα.

It can be both literal and idiomatic.

Literally, βαρύς / βαριά / βαρύ means heavy.

But with food and drink, it often means:

• rich
• heavy on the stomach
• too much
• hard to digest
• sometimes even too strong

So here της φαίνεται πολύ βαρύ most likely means something like:

• she finds it too heavy
• she thinks it’s too rich
• it feels too much for her

That is a very natural use in Greek.

Because αλλά means but, and it connects two contrasting clauses.

The two parts are:

1. Μου αρέσει το αφρόγαλα στον καπουτσίνο
2. αλλά η αδερφή μου λέει ότι της φαίνεται πολύ βαρύ

So the comma helps separate the two ideas:

• I like the milk foam in cappuccino, but my sister says it seems too heavy to her.

This punctuation works much like English.

Yes, especially the repeated subject.

In της φαίνεται πολύ βαρύ, Greek does not repeat το αφρόγαλα, because it is already clear from context.

A fuller version could be:

• η αδερφή μου λέει ότι το αφρόγαλα τής φαίνεται πολύ βαρύ

But that sounds more explicit. The original sentence is more natural and less repetitive.

Greek often leaves things understood when the context is clear.