Zločin je ozbiljan.

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

So:

• Zločin = crime
• je = is
• ozbiljan = serious

Croatian often uses je just like English uses is in sentences such as The crime is serious.

Because ozbiljan is an adjective and it has to agree with the noun zločin.

Here, zločin is:

• masculine
• singular
• in the nominative

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

• ozbiljan = serious

If the noun changed, the adjective would change too. For example:

• problem je ozbiljan = the problem is serious
• situacija je ozbiljna = the situation is serious
• pitanje je ozbiljno = the question/issue is serious

In Croatian, nouns have grammatical gender: masculine, feminine, or neuter.

Zločin is a masculine noun. One clue is that many masculine nouns in the nominative singular end in a consonant, and zločin does.

That does not mean every noun ending in a consonant is masculine without exception, but it is a very common pattern.

Because zločin is masculine, the adjective must match it:

• zločin je ozbiljan

No. Croatian does not have articles like English a/an and the.

So Zločin je ozbiljan could mean:

• A crime is serious
• The crime is serious
• Crime is serious

Which interpretation is correct depends on context.

This is the most neutral, standard word order:

• noun + je + adjective

Croatian word order is more flexible than English, so other orders are possible for emphasis or style, such as:

• Ozbiljan je zločin
• Zločin ozbiljan je (much less natural in ordinary speech)

But Zločin je ozbiljan is the normal, straightforward version a learner should start with.

Normally, no. In this kind of present-tense statement, je is usually required.

So you say:

• Zločin je ozbiljan.

Not normally:

• Zločin ozbiljan.

Croatian can sometimes omit forms of to be in special styles, headlines, or poetry, but in ordinary standard sentences you should keep je.

It can describe both people and things.

Ozbiljan can mean serious in several senses, including:

• a serious person
• a serious problem
• a serious illness
• a serious crime

So zločin je ozbiljan is completely natural Croatian.

A rough pronunciation is:

• zlo-chin

More precisely:

• zl as in z
  • l
• o as a short clear o
• č sounds like ch in church
• i like ee in see, but shorter
• n as in English n

So zločin sounds approximately like ZLO-chin.

Also, č and ć are different Croatian letters, and here it is č.

Both the noun and the adjective are in the nominative singular here.

Why?

Because this is a basic sentence of the type:

• X is Y

The subject zločin is in the nominative, and the predicate adjective ozbiljan agrees with it in gender, number, and case.

So:

• zločin = nominative singular masculine
• ozbiljan = nominative singular masculine

Yes. The adjective would change to match the gender of the noun.

Examples:

• Situacija je ozbiljna. = The situation is serious.

  • situacija is feminine
  • so the adjective is ozbiljna

• Pitanje je ozbiljno. = The question/issue is serious.

  • pitanje is neuter
  • so the adjective is ozbiljno

With zločin, which is masculine, you use:

• ozbiljan

Yes. Because Croatian has no articles, the noun can sometimes be understood in a general or abstract sense depending on context.

So Zločin je ozbiljan might refer to:

• a particular crime
• crime as a category
• the concept of crime in a certain discussion

In real use, context tells you which meaning is intended.