La vacant és nova.

Here, vacant is a noun, not an adjective. It means something like vacancy or open position.

You can tell because it has the article la in front of it and acts as the subject of the sentence:

• La vacant = the vacancy
• és nova = is new

In other contexts, vacant can also be an adjective:

• una plaça vacant = an open / vacant position

Because vacant is feminine in Catalan when used as this noun.

Catalan nouns have grammatical gender, so you need the feminine article:

• la vacant = the vacancy

Even though the word does not end in -a, it is still feminine. This is normal in Catalan: gender is not always predictable from the ending, so it is best to learn nouns together with their article.

Because adjectives in Catalan usually agree in gender and number with the noun they describe.

Since vacant is feminine singular, the adjective must also be feminine singular:

• nou = masculine singular
• nova = feminine singular
• nous = masculine plural
• noves = feminine plural

So:

• La vacant és nova.

and not:

• La vacant és nou.

És is the 3rd person singular form of ser, meaning is.

The accent is part of the correct spelling:

• és = is

This also helps distinguish it from es, which is a different word in Catalan.

So the accent is not optional here.

Catalan uses ser for many basic descriptions and identifications, including saying that something is new.

So:

• La vacant és nova. = The vacancy is new.

Using estar here would sound unnatural in standard Catalan. In general, ser is used for identity, classification, and many descriptions, while estar is used in more limited situations, such as location or some temporary/resulting states.

Because Catalan normally uses the definite article the same way English uses the in a sentence like The vacancy is new.

So:

• la vacant = the vacancy

Leaving the article out would not sound natural in a normal sentence like this.

Yes. Vacant can be either a noun or an adjective, depending on the sentence.

As a noun:

• la vacant = the vacancy

As an adjective:

• una plaça vacant = an open / vacant position
• un càrrec vacant = a vacant post

In La vacant és nova, it is clearly a noun.

Because La nova vacant is just a noun phrase meaning the new vacancy. It is not a complete sentence by itself in the same way.

If you want to say The vacancy is new, you need the verb és:

• La vacant és nova.

Compare:

• la nova vacant = the new vacancy
• la vacant és nova = the vacancy is new

So the position of nova changes the structure.

The structure is:

• La vacant = subject
• és = verb
• nova = predicate adjective

So it follows a very familiar pattern:

Subject + verb + adjective

This is similar to English:

• The vacancy is new.

In this sentence, nova is a predicate adjective. That means it describes the subject through the verb és.

So:

• La vacant és nova. = The vacancy is new.

This is different from an adjective placed directly next to the noun:

• la nova vacant = the new vacancy

Both are grammatical, but they mean slightly different things structurally.