Ovo područje je veliko.

Because ovo has to agree with područje, and područje is neuter singular.

In Croatian, words like this change form depending on gender, number, and case:

• ovaj = masculine singular
• ova = feminine singular
• ovo = neuter singular

So:

• ovaj grad = this city
• ova kuća = this house
• ovo područje = this area

Here, ovo matches područje.

A very common clue is the ending -e or -o in the singular nominative. Many Croatian nouns with those endings are neuter.

So područje is a neuter noun, which is why it takes:

• ovo for this
• veliko for big

A dictionary will usually mark it as neuter, but the ending is already a strong hint.

Because adjectives in Croatian must agree with the noun they describe.

Since područje is:

• neuter
• singular
• nominative

the adjective must also be neuter singular nominative, which gives veliko.

Compare:

• velik grad = a big city / the city is big?
  
  • as a basic masculine form
• velika kuća = a big house
• veliko područje = a big area

In this sentence, veliko is a predicate adjective after je, but the agreement rule is the same.

Je is the 3rd person singular present tense of biti = to be.

So it corresponds to is.

Forms of biti in the present tense are:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is
• mi smo = we are
• vi ste = you are
• oni/one/ona su = they are

In Ovo područje je veliko, je connects the subject ovo područje with the description veliko.

Because here the adjective is not directly attached to the noun inside one noun phrase. It is part of the predicate.

There is a difference between:

• veliko područje = a big area
• ovo područje je veliko = this area is big

So:

• before the noun: attributive adjective
• after je: predicate adjective

Both are normal, but they mean slightly different things grammatically.

Yes, but that is a different structure.

• Ovo područje je veliko = this area is big
• Ovo je veliko područje = this is a big area

In the first sentence, ovo područje is the subject as a full noun phrase.
In the second, ovo stands on its own as this, and veliko područje is what it is identified as.

Both are correct, but they are not interchangeable in every context.

It is in the nominative singular.

Why? Because it is the subject of the sentence:

• ovo područje = the thing being talked about
• je veliko = is big

The nominative is the usual case for the subject of a sentence.

Because Croatian does not have articles like English the and a/an.

Instead, Croatian expresses definiteness through:

• context
• word order
• demonstratives like ovaj / ova / ovo = this
• sometimes just the general meaning of the sentence

So područje can mean area, an area, or the area, depending on context.
In this sentence, ovo already makes it specific: this area.

In a sentence like ovo područje, it functions like a demonstrative determiner or demonstrative adjective in English terms, because it comes before a noun and specifies it.

Some Croatian grammar traditions classify these forms under demonstrative pronouns, even when they stand next to nouns. So you may see different terminology.

The important practical point is:

• ovo changes form to agree with the noun
• here it means this
• here it modifies područje

Roughly: POH-droo-chyeh, though exact stress can vary.

A few helpful sound notes:

• č sounds like ch in church
• j sounds like English y in yes
• Croatian spelling is fairly phonetic, so words are usually pronounced close to how they are written

So područje has the sound sequence čj, which can feel a little awkward at first, but it becomes easier with practice.

Yes, Croatian word order is more flexible than English, though not completely free.

The neutral, straightforward order is:

• Ovo područje je veliko.

You may also see different orders for emphasis, but they can sound marked or stylistic depending on context.

For learners, the best choice is to keep the normal pattern:

• subject + je + adjective

That makes your sentence clear and natural.

Yes. That is one of the most important grammar patterns in Croatian.

Both the demonstrative and the adjective agree with the noun:

• ovo matches područje
• veliko also matches područje

Since područje is neuter singular nominative, both words appear in their neuter singular nominative forms.

This kind of agreement is very common in Croatian, so getting used to it early is extremely useful.