On je blizanac.

• On = he
• je = is
• blizanac = twin (masculine singular)

So the sentence literally matches English quite closely: He is a twin.

Je is the 3rd person singular present tense of the verb biti (to be).

So:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is

In On je blizanac., je links the subject on with the noun blizanac, just like is in English.

Normally, no in this kind of standard sentence.

Croatian often drops subject pronouns, but it usually does not drop the present-tense form of to be in a basic sentence like this.

So these are natural:

• On je blizanac. = He is a twin.
• Je blizanac. is not normal standard Croatian.
• Blizanac je. can work in context, but je is still there.

What can be omitted is the pronoun on, if the context already makes the subject clear:

• On je blizanac.
• Je blizanac? is not standard as a statement, but in questions the structure changes.
• Blizanac je. = He is a twin. / A twin, he is. (contextual/emphatic)

Most neutral full sentence: On je blizanac.

Croatian has no articles like English a / an / the.

So blizanac can mean:

• a twin
• sometimes the twin, depending on context

In this sentence, English usually translates it as He is a twin.

This is very common in Croatian. For example:

• On je učitelj. = He is a teacher.
• Ona je liječnica. = She is a doctor.

Blizanac is in the nominative singular masculine form.

That is the basic dictionary form, and it is used here because it is the predicate noun after je in this simple identification sentence.

Useful related forms:

• blizanac = twin (masculine singular)
• blizanca = of a twin / twin (accusative or genitive singular, depending on context)
• blizanci = twins (masculine plural)

A learner may notice the ending -ac, which is a normal masculine noun ending in Croatian.

The feminine form is blizanka.

So:

• On je blizanac. = He is a twin.
• Ona je blizanka. = She is a twin.

Plural forms:

• Oni su blizanci. = They are twins.
• One su blizanke. = They are twins. (all-female group)

The neutral word order is exactly:

• On je blizanac.

Croatian word order is fairly flexible, but je is a clitic, and clitics usually go in the second position in the sentence or clause.

So:

• On je blizanac. = neutral, standard
• Blizanac je. = possible, more context-dependent
• On blizanac je. = not natural

For a beginner, the safest pattern is:

subject + je + noun/adjective

Yes, but it is more contextual and less neutral than On je blizanac.

Blizanac je might be used when the subject is already understood:

• Tvoj brat? Blizanac je. = Your brother? He’s a twin.

But if you are simply learning the standard full sentence, On je blizanac. is the best version.

A rough pronunciation is:

BLI-za-nats

A few helpful sound notes:

• j in Croatian sounds like English y in yes
• c sounds like ts
• z sounds like z in zoo

So:

• je sounds roughly like ye
• blizanac ends with -nats, not -nak or -nas

A rough full pronunciation:

On ye BLI-za-nats.

Not always. Croatian often drops subject pronouns when the meaning is clear from context.

So both can occur:

• On je blizanac. = He is a twin.
• Blizanac je. = He is a twin. (if the subject is already clear)

However, learners are often shown on because it makes the sentence easier to understand and translate.

Including on can also add emphasis or contrast:

• On je blizanac, a ona nije. = He is a twin, and she isn’t.

You change both the pronoun and the verb, and usually the noun too:

• Oni su blizanci. = They are twins.

Breakdown:

• oni = they
• su = are
• blizanci = twins

For an all-female group:

• One su blizanke.

A common way is:

• Je li on blizanac? = Is he a twin?

You may also hear:

• Je l’ on blizanac? = informal spoken version

Useful pattern:

• Je li on ... ? = Is he ... ?
• Je li ona ... ? = Is she ... ?

So:

• Je li ona blizanka? = Is she a twin?

Yes, blizanac is grammatically masculine, so it is used for a male twin.

For a female twin, use blizanka:

• On je blizanac.
• Ona je blizanka.

If you want to talk about twins in general or a mixed group, use the plural masculine form:

• blizanci

Yes, it is a completely natural and correct sentence.

It is simple, standard Croatian and good for beginners because it shows:

• the pronoun on
• the verb je
• a masculine singular noun blizanac

So it is both grammatically correct and natural in everyday language.