Learn Hardcore Croatian: Ovo je moja knjiga.

ovo is a demonstrative pronoun (neuter singular) that functions like English “this” in the sentence “This is my book.” It stands alone, pointing to whatever object you’re referring to.

Why is it ovo (neuter) and not ova (feminine), since knjiga is feminine?

When you use a demonstrative pronoun by itself (“this is…”), Croatian always uses the neuter form ovo regardless of the gender of the noun in the predicate. If you wanted a demonstrative adjective modifying knjiga, you’d say “ova knjiga”, but here ovo doesn’t modify knjiga directly—it acts as the subject “this (thing).”

What role does je play in this sentence? Can you leave it out?

je is the 3rd-person-singular present of the copular verb biti (“to be”). In a simple identification sentence (“This is X”), the verb je is required to link subject and predicate. You cannot omit it in standard Croatian.

Why is moja used instead of moj or moje?

moja is the feminine singular form of the possessive adjective moj (“my”). It agrees in gender (feminine), number (singular), and case (nominative) with knjiga, which is feminine singular.

In what case is knjiga and why?

knjiga is in the nominative singular. In a sentence of the form “This is my book,” both the subject pronoun (ovo) and the predicate noun (knjiga) appear in the nominative case.

How would you ask “Is this my book?” using the same words?

You insert the question particle li after the verb:
Je li ovo moja knjiga?
Literally: “Is (it) this my book?” You can also use rising intonation:
Ovo je moja knjiga?

Can I change the word order? For example, moja knjiga je ovo?

That word order is grammatically possible but sounds odd. The neutral, idiomatic pattern for “This is my book” is Ovo je moja knjiga.

Where is the stress in knjiga, and how do you pronounce the knj cluster?

knjiga is pronounced [kɲĭːɡa], with the primary stress on the first syllable (KNI-ga). The cluster knj is a single palatal consonant [kɲ], like the “kn” in English “canyon,” followed by i.

What’s the difference between ovo and to as demonstratives?

ovo = “this” (something physically or contextually close)
to = “that” (something more remote, either physically or in discourse)
So Ovo je moja knjiga points to a nearby book, whereas To je moja knjiga would mean “That is my book.”