Η αγκαλιά της μαμάς μου είναι η καλύτερη.

Αγκαλιά is a feminine noun that usually means:

• a hug / embrace (the action or the state of being held), and
• sometimes someone’s arms, as in “in my mother’s arms”.

Common expressions:

• δίνω μια αγκαλιά – I give a hug
• παίρνω κάποιον αγκαλιά – I take someone in my arms / I hug someone
• στην αγκαλιά της μαμάς μου – in my mom’s arms

So in this sentence, η αγκαλιά refers to “the hug / embrace (from her).”

Greek doesn’t usually use a possessive adjective in front of a noun (like my hug) the way English does.
Instead, it often uses:

[definite article] + [noun] + [possessor in the genitive]

So:

• η αγκαλιά της μαμάς μου
  = “the hug of my mom” / “my mom’s hug”

Literally:

• η – the (feminine, singular)
• αγκαλιά – hug
• της μαμάς μου – of my mom

To say “my hug” (the hug that belongs to me), you would say:

• η αγκαλιά μου

But here, we want “the hug of my mom,” so we use της μαμάς μου.

They are doing different jobs:

• της here is the genitive definite article (feminine singular): “of the”.
• μαμάς is the noun “mom” in the genitive case.
• μου is the weak personal pronoun “my”.

So της μαμάς μου literally is “of the mom of me,” i.e. “my mom’s”.

You can think of it as:

• της μαμάς – of the mom
• μου – my

Greek often stacks possessors like this:

• το βιβλίο της φίλης μου – the book of my friend / my friend’s book
• το σπίτι του αδερφού μου – my brother’s house

You cannot normally drop της here; μαμάς μου alone would sound wrong.

Μαμάς is the genitive singular of μαμά (“mom”).

• μαμά – nominative (subject form): “mom”
• της μαμάς – genitive: “of (the) mom”

In this sentence, “mom” is not the subject; she is the possessor (“the hug of my mom”), so Greek uses the genitive:

• της μαμάς μου – of my mom

So the -ς (sigma) at the end of μαμάς marks the genitive form.

Αγκαλιά is:

• Gender: feminine
• Number: singular

Clues:

1. The article η is the feminine singular definite article.
2. Many feminine nouns in the nominative singular end in -α or -η:
   
   • η αγκαλιά – the hug
   • η καρδιά – the heart
   • η χώρα – the country

So η αγκαλιά = “the (one) hug/embrace” (feminine, singular).

The first η goes with αγκαλιά:

• η αγκαλιά – the hug

The second η goes with καλύτερη, which acts like a noun phrase here:

• η καλύτερη – the best (one)

Greek very often keeps the article in superlative expressions:

• είναι ο καλύτερος – he is the best
• είναι η καλύτερη – she/it (fem.) is the best
• είναι το καλύτερο – it (neuter) is the best

In our sentence, η καλύτερη really means “the best (hug)”, with αγκαλιά understood, not repeated.

Because καλύτερη has to agree in gender and number with the understood noun, which is αγκαλιά (feminine singular).

• η αγκαλιά → feminine singular
• So the adjective/superlative must be: η καλύτερη (feminine singular)

If the noun were masculine:

• ο φίλος μου είναι ο καλύτερος – my friend is the best (masc.)

If the noun were neuter:

• το σπίτι μου είναι το καλύτερο – my house is the best (neuter)

Here the structure is:

• Η αγκαλιά (της μαμάς μου) είναι η καλύτερη (αγκαλιά).
  “The hug (of my mom) is the best (hug).”

Είναι is:

• 3rd person, singular
• Present tense
• Of the verb είμαι – “to be”

Greek normally omits subject pronouns when they’re clear from context:

• (Αυτή) είναι η καλύτερη. – (She) is the best.
• (Αυτή η αγκαλιά) είναι η καλύτερη. – (This hug) is the best.

So the logical subject is η αγκαλιά της μαμάς μου, and είναι just links subject and complement, like English “is”.

Καλύτερη is the synthetic comparative/superlative of καλή (“good”):

• καλή – good
• καλύτερη – better / best

Πιο καλή literally means “more good”. It’s also used, but with this adjective, καλύτερη is more natural and idiomatic.

You could say:

• Η αγκαλιά της μαμάς μου είναι η πιο καλή.

It would be understood, but:

• η καλύτερη sounds more natural and is what Greek speakers would typically prefer here.

Yes, you can change the structure and still be correct, though the nuance shifts slightly.

Original:

• Η αγκαλιά της μαμάς μου είναι η καλύτερη.
  Focus on the hug itself: “My mom’s hug is the best.”

Alternative:

• Η μαμά μου έχει την καλύτερη αγκαλιά.
  Literally: “My mom has the best hug.”
  Slightly more focus on your mom as the possessor of “the best hug”.

Both are natural; they just frame the idea differently. The original sentence is perfectly normal, clear Greek.

Yes:

• μαμά – very common, informal, affectionate: “mom / mommy / mum”.
• μητέρα – more formal, neutral: “mother”.

You could say:

• Η αγκαλιά της μητέρας μου είναι η καλύτερη.

That is grammatically correct but sounds more formal / distant.
For the warm, emotional tone implied by this sentence, μαμά is the most natural choice.