Broșa este autentică.

• Broșa = the brooch. It is the subject of the sentence.
• este = is. It is the 3rd person singular form of a fi (to be).
• autentică = authentic / genuine. It is an adjective describing broșa.

So the structure is very similar to English: subject + verb + adjective.

Because broșa is the definite form, meaning the brooch.

In Romanian, the definite article is usually attached to the end of the noun instead of being a separate word like English the.

For this noun:

• o broșă = a brooch
• broșa = the brooch

So the -a at the end is functioning as the definite article here.

Because Romanian adjectives must agree with the noun in gender and number.

Broșa is a feminine singular noun, so the adjective must also be feminine singular:

• masculine singular: autentic
• feminine singular: autentică

That is why you get:

• un obiect autentic = an authentic object
• o broșă autentică = an authentic brooch

Broșă is a feminine noun.

You can often tell this from the article and adjective agreement:

• o broșă
• broșa
• autentică

All of those point to feminine singular.

These are two Romanian letters that English speakers often notice right away:

• ș is pronounced like sh in shoe
• ă is a short central vowel, somewhat like the a in sofa or about, but shorter and more neutral

So:

• Broșa sounds roughly like BRO-sha
• autentică sounds roughly like ow-TEN-ti-kuh, with the final ă being very short and neutral

These English approximations are not perfect, but they are a useful starting point.

Yes. E is a very common short form of este in everyday Romanian.

So both are correct:

• Broșa este autentică.
• Broșa e autentică.

The version with e is more natural in casual speech, while este can sound a bit more full or formal.

The normal, neutral word order is:

Broșa este autentică.

Romanian does allow some flexibility in word order, but changing it usually changes the emphasis.

For example:

• Autentică este broșa. = more marked, more literary, or emphasizing authentică
• Este autentică broșa? = can sound like a question depending on intonation and context

So for a basic statement, Broșa este autentică is the standard order to learn first.

Normally, no. In standard Romanian, you usually keep the verb a fi in sentences like this.

So:

• correct: Broșa este autentică.
• very common in speech: Broșa e autentică.

But simply saying Broșa autentică would not normally work as a complete standard sentence meaning The brooch is authentic.

You would use the indefinite article:

• O broșă este autentică. = A brooch is authentic / One brooch is authentic

More naturally in many contexts, you might also say:

• Această broșă este autentică. = This brooch is authentic
• Broșa aceasta este autentică. = This brooch is authentic

The key contrast is:

• broșa = the brooch
• o broșă = a brooch

The plural would be:

Broșele sunt autentice. = The brooches are authentic.

Notice the changes:

• broșa → broșele
• este → sunt
• autentică → autentice

This shows agreement in both number and gender/form.

A helpful guide is:

• bróșa — stress on the first syllable
• auténtică — stress on ten

So you can think of the rhythm roughly as:

• BRÓ-sha
• ow-TÉN-ti-kuh

Stress is important in Romanian, even though it is not usually marked in normal spelling.