Αυτό το μαξιλάρι είναι πολύ μαλακό.

Because Greek often uses both a demonstrative and the definite article together.

• Αυτό = this
• το = the
• μαξιλάρι = pillow

So Αυτό το μαξιλάρι literally looks like this the pillow, but it simply means this pillow.

This is completely normal in Greek:

• αυτό το βιβλίο = this book
• αυτή η καρέκλα = this chair
• αυτό το σπίτι = this house

You usually do not say just Αυτό μαξιλάρι.

Because μαξιλάρι is a neuter noun in Greek.

Greek nouns have grammatical gender:

• masculine
• feminine
• neuter

The demonstrative must match the noun’s gender:

• αυτός = this (masculine)
• αυτή = this (feminine)
• αυτό = this (neuter)

Since μαξιλάρι is neuter, you use αυτό.

For the same reason: μαξιλάρι is neuter singular, so it takes the neuter singular article το.

Compare:

• ο καναπές = the sofa (masculine)
• η κουβέρτα = the blanket (feminine)
• το μαξιλάρι = the pillow (neuter)

So:

• αυτός ο καναπές
• αυτή η κουβέρτα
• αυτό το μαξιλάρι

Because adjectives in Greek usually agree with the noun they describe in:

• gender
• number
• case

Here, μαξιλάρι is:

• neuter
• singular
• nominative (the subject of the sentence)

So the adjective also appears in the neuter singular nominative form:

• masculine: μαλακός
• feminine: μαλακή
• neuter: μαλακό

So:

• Ο καναπές είναι πολύ μαλακός.
• Η κουβέρτα είναι πολύ μαλακή.
• Το μαξιλάρι είναι πολύ μαλακό.

είναι means is.

In this sentence, it links the subject to the description:

• Αυτό το μαξιλάρι = the subject
• είναι = is
• πολύ μαλακό = very soft

So Greek works like English here:

• This pillow is very soft.

Yes, in a normal full sentence like this, you generally need είναι.

Here πολύ means very.

It modifies the adjective μαλακό:

• μαλακό = soft
• πολύ μαλακό = very soft

A useful thing to know is that πολύ can also be related to much/a lot, depending on context, but in front of an adjective it often means very.

Examples:

• πολύ καλός = very good
• πολύ μεγάλο = very big
• πολύ όμορφη = very beautiful

In this sentence, μαλακό is an adjective, because it describes a noun: the pillow.

Greek distinguishes between:

• adjectives, which describe nouns
• adverbs, which describe verbs, adjectives, or whole clauses

Here you need the adjective form because you are saying what the pillow is like.

So:

• μαλακό = soft

If you were talking about doing something softly/gently, Greek would use a different structure or a different adverb, depending on the context.

Greek word order is more flexible than English, although not completely free.

The neutral, natural order here is:

• Αυτό το μαξιλάρι είναι πολύ μαλακό.

You may also hear variations for emphasis, such as:

• Πολύ μαλακό είναι αυτό το μαξιλάρι.

That sounds more marked, like This pillow is really soft or Very soft, this pillow is.

For learners, it is best to stick with:

• subject + είναι + description

Yes, that is possible.

• Αυτό το μαξιλάρι is the most straightforward and common way to say this pillow.
• Το μαξιλάρι αυτό is also grammatical, but it can sound slightly more emphatic or stylistically different depending on context.

For everyday learning, use:

• Αυτό το μαξιλάρι

A learner-friendly pronunciation guide would be:

af-TO to maxi-LA-ri EE-ne po-LEE mala-KO

A few notes:

• Αυτό has the stress on the last syllable: -τό
• μαξιλάρι has the stress on λά
• είναι is commonly pronounced roughly EE-ne
• πολύ has the stress on λύ
• μαλακό has the stress on the final -κό

The accent marks in Greek show where the stress goes.

The accent mark shows which syllable is stressed when you pronounce the word.

In this sentence:

• Αυτό
• μαξιλάρι
• είναι
• πολύ
• μαλακό

Each accent tells you where to place the stress.

This matters because correct stress is an important part of sounding natural in Greek, and sometimes it can even help distinguish forms.

μαξιλάρι is inherently a neuter noun, so its grammatical gender does not change.

That means you normally say:

• το μαξιλάρι
• ένα μαξιλάρι
• αυτό το μαξιλάρι

And adjectives referring to it must match in the appropriate neuter form:

• μαλακό
• μεγάλο
• μικρό
• άνετο

It is in the nominative singular, because it is the subject of the sentence.

• Αυτό το μαξιλάρι = the thing being talked about
• είναι πολύ μαλακό = what is being said about it

For many neuter nouns, the nominative and accusative singular look the same, so learners often do not see a visible change right away.

Normally, no.

In standard Greek, when you use this/that before a noun, you usually also use the article:

• αυτό το μαξιλάρι = this pillow
• εκείνο το μαξιλάρι = that pillow

So Αυτό μαξιλάρι sounds incomplete or nonstandard to a learner’s ear. Use Αυτό το μαξιλάρι.

Everything that agrees with the noun would change.

Examples:

Masculine:

• Αυτός ο καναπές είναι πολύ μαλακός.
• This sofa is very soft.

Feminine:

• Αυτή η κουβέρτα είναι πολύ μαλακή.
• This blanket is very soft.

Neuter:

• Αυτό το μαξιλάρι είναι πολύ μαλακό.
• This pillow is very soft.

So the demonstrative, article, and adjective all change to match the noun.