Αυτό είναι δικό μου βιβλίο.

This is my own book.

Breakdown of Αυτό είναι δικό μου βιβλίο.

• είμαι: to be
• αυτός: this
• μου: my
• το βιβλίο: the book
• δικός: own

Questions & Answers about Αυτό είναι δικό μου βιβλίο.

Why does the sentence use both δικό and μου? Isn’t μου already “my”?

Μου by itself is the weak (clitic) possessive, like “my” in το βιβλίο μου (my book).

Δικός / δική / δικό plus μου is the strong possessive, roughly like “mine / my own”:

• το βιβλίο μου = my book (neutral statement of ownership)
• το δικό μου βιβλίο = my own book / my book (as opposed to someone else’s)

In Αυτό είναι δικό μου βιβλίο, δικό μου adds emphasis:
“This is a book that is mine (my own), not someone else’s.”

Could I just say Αυτό είναι το βιβλίο μου instead? Is there a difference?

Yes, you can, and it is very common:

• Αυτό είναι το βιβλίο μου. = This is my book. (neutral)
• Αυτό είναι δικό μου βιβλίο. = This is my own book / This is a book of mine (with contrast or emphasis: it belongs to me, not to someone else).

So:

• Use το βιβλίο μου for ordinary “my book”.
• Use δικό μου βιβλίο (or το δικό μου βιβλίο) when you want to stress whose it is, often in contrast:
  • Όχι, αυτό είναι το δικό μου βιβλίο.
    No, this is my book. (not yours / not his)

Why is it δικό and not δικός or δική?

Because δικός / δική / δικό must agree in gender, number, and case with the noun it refers to.

• βιβλίο is neuter singular, so you need the neuter singular form:
  • masculine: δικός μου φίλος (my friend – male)
  • feminine: δική μου τσάντα (my bag)
  • neuter: δικό μου βιβλίο (my book)

So with βιβλίο you must use δικό (not δικός or δική).

What exactly is the structure here? Which word is the subject and which is the “book” part?

The structure is:

• Αυτό – subject (demonstrative pronoun: “this”)
• είναι – verb “to be” (3rd person singular)
• δικό μου βιβλίο – predicate (saying what “this” is)

Inside the predicate:

• βιβλίο – the noun (“book”)
• δικό μου – possessive phrase modifying βιβλίο (“my own”)

So the basic pattern is:
Αυτό (subject) είναι (verb) δικό μου βιβλίο (predicate).
“This is a book of mine.”

Why is there no word for “a” before βιβλίο?

Modern Greek can use an indefinite article (ένας / μία / ένα), but it is often omitted, especially:

• in predicate positions after είμαι, and
• when possession is already clear.

Compare:

• Αυτό είναι βιβλίο. = This is a book.
• Αυτό είναι ένα βιβλίο. = This is a book (slightly more explicit / often “one book”).
• Αυτό είναι δικό μου βιβλίο. = This is a book of mine.
• Αυτό είναι ένα δικό μου βιβλίο. = This is one of my books.

Your sentence is natural without an “a”; Greek simply doesn’t require it here.

What case is βιβλίο in here?

Βιβλίο is neuter singular nominative.

With the verb είμαι, the complement of the subject (the “X” in “This is X”) is normally in the nominative case, just like the subject:

• Αυτό – nominative (subject)
• βιβλίο – nominative (subject complement / predicate noun)

For neuter nouns, nominative and accusative look the same (βιβλίο), which can make this less obvious, but grammatically it is nominative.

What exactly is Αυτό doing here? Is it “this book” or just “this”?

In this sentence Αυτό is a demonstrative pronoun, meaning simply “this” (thing), and it is the grammatical subject:

• Αυτό = this (one / thing)
• είναι δικό μου βιβλίο = is a book of mine

So we literally have:
“This (thing) is a book of mine.”

If you wanted to say “this book is mine”, you would normally use:

• Αυτό το βιβλίο είναι δικό μου.
  This book is mine.

Is είναι always necessary here, or can it be dropped?

In normal, complete sentences, είναι is required:

• Αυτό είναι δικό μου βιβλίο. ✅
• Αυτό δικό μου βιβλίο. ❌ (ungrammatical as a full sentence)

You can drop είναι only in:

• very short ellipses (signs, headlines, note-taking), or

• conversational fragments where the verb is understood:

  • (Τί είναι αυτό;) – Δικό μου βιβλίο.
    (What’s this?) – My book.

But as a standard sentence, you say Αυτό είναι …

Can I leave out βιβλίο and just say Αυτό είναι δικό μου?

Yes, and that is very natural.

• Αυτό είναι δικό μου. = This is mine.

Here δικό μου stands alone as a strong possessive pronoun (“mine”). The noun is understood from context (book, pen, bag, etc.).

You cannot do that with μου alone:

• Αυτό είναι μου. ❌ (wrong)
• Αυτό είναι δικό μου. ✅ (correct: This is mine.)

How is δικό μου pronounced? Does μου have its own stress?

Pronunciation (in IPA): δικό μου → [ðiˈko mu]

• The stress is on -κό of δικό.
• Μου is a clitic (weak, unstressed word) and does not get its own stress.
• In speech they flow together like one unit: δι-KÓ-mu.

The written accent on δικό marks the single stress for the whole phrase δικό μου.

Is the word order fixed? Could I say Αυτό το βιβλίο είναι δικό μου or Αυτό είναι βιβλίο δικό μου?

Greek word order is flexible, but there are more natural patterns:

1. Αυτό το βιβλίο είναι δικό μου. ✅
   Very common:

   • literally: “This book is mine.”
   • Αυτό το βιβλίο = this book (subject)
   • είναι δικό μου = is mine

2. Αυτό είναι δικό μου βιβλίο. ✅
   Your original:

   • literally: “This is a book of mine.” (with emphasis on it being yours)

3. Αυτό είναι βιβλίο δικό μου.
   Possible, but sounds marked / literary / very emphatic in modern speech. It moves δικό μου after βιβλίο for strong focus.

For everyday use, the most typical options would be:

• Αυτό είναι το βιβλίο μου.
• Αυτό το βιβλίο είναι δικό μου.
• Αυτό είναι δικό μου. (without naming the noun)

What’s the difference between δικό μου βιβλίο and το δικό μου βιβλίο?

Both contain the strong possessive δικό μου, but:

• το δικό μου βιβλίο

  • has the definite article το,
  • clearly means “my (specific) book”,
  • is very natural and common:
    • Αυτό είναι το δικό μου βιβλίο.
      This is my book (as opposed to someone else’s).

• δικό μου βιβλίο (without το)

  • is less tightly definite, can feel like “a book of mine / my own book”,
  • often appears in contrasts or more “descriptive” contexts:
    • Αυτό είναι δικό μου βιβλίο, όχι δανεικό.
      This is my own book, not a borrowed one.

So in everyday speech, when you just want to say “this is my book (not yours)”, Αυτό είναι το δικό μου βιβλίο is the most straightforward emphatic form.