Broj je na obrascu.

Because na here means on in the sense of location, and with that meaning it requires the locative case.

• dictionary form: obrazac = form
• locative singular: na obrascu = on the form

So:

• obrazac = the basic form of the noun
• na obrascu = after the preposition na when talking about where something is

This is a very common pattern in Serbian:

• na stolu = on the table
• na papiru = on the paper
• na obrascu = on the form

Obrascu is in the locative singular.

The noun obrazac is masculine, and after na expressing location, it changes to the locative:

• nominative: obrazac
• locative: na obrascu

In many Serbian grammar descriptions, na can take:

• locative for location: na obrascu = on the form
• accusative for movement toward something: na obrazac = onto the form / onto the document, depending on context

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

So:

• broj = number
• je = is
• na obrascu = on the form

Together: Broj je na obrascu.

In Serbian, the present tense of to be is often expressed explicitly in sentences like this, just as in English:

• On je ovde. = He is here.
• Knjiga je na stolu. = The book is on the table.

Usually, no, not in a normal statement like this.

Broj na obrascu by itself sounds incomplete if you mean The number is on the form. Without je, it is more like a noun phrase, such as:

• the number on the form

So the full sentence needs je:

• Broj je na obrascu.

This is different from Russian, where the present-tense to be is often omitted. In Serbian, it is normally kept in this kind of sentence.

Serbian has no articles like a or the.

So broj can mean:

• a number
• the number

and obrazac can mean:

• a form
• the form

The exact meaning depends on context.

That means Broj je na obrascu could be understood as:

• The number is on the form
• A number is on the form

In real use, context usually makes it clear which one is intended.

Yes, Serbian word order is fairly flexible, although Broj je na obrascu is the most neutral order.

Possible variations include:

• Broj je na obrascu. = neutral
• Na obrascu je broj. = puts more focus on on the form
• Na obrascu broj je... = generally less natural by itself

One important point: je is a clitic, and clitics in Serbian usually go in the second position of the sentence or clause.

That is why you often see:

• Broj je na obrascu.
• Na obrascu je broj.

In both cases, je comes very early.

A simple approximate pronunciation is:

broy yeh nah OH-brahs-tsoo

A few details:

• broj sounds roughly like broy
• je sounds like yeh
• na sounds like nah
• obrascu has c pronounced like ts, so obra-s-tsu overall becomes something like OH-brahs-tsoo

The j in Serbian is pronounced like English y in yes.

Here na means on in a physical or document-related sense.

So na obrascu means:

• on the form
• in the form, depending on English style and context

Serbian often uses na where English may use either on or in with documents, pages, lists, forms, and similar things.

For example:

• na papiru = on the paper
• na spisku = on the list
• na obrascu = on the form

So even if English sometimes prefers in the form, Serbian naturally uses na here.

Broj is a masculine noun meaning number.

Its basic singular form is:

• broj

In this sentence it is in the nominative singular, because it is the subject of the sentence:

• Broj je na obrascu. = The number is on the form.

A few related forms:

• broja = genitive singular
• broju = dative/locative singular
• brojem = instrumental singular

You do not need all of these to understand the sentence, but it helps to know that broj is the subject, while obrascu changes because it follows na.

Yes. Obrazac is a common formal word for a form, especially an official or administrative one.

It can refer to things like:

• an application form
• a registration form
• a printed or digital official form

So na obrascu is exactly the kind of phrase you would expect in office, school, government, or paperwork contexts.

Sometimes, yes, depending on context, but The number is on the form is usually the most direct translation.

Serbian uses na obrascu, and English often says on the form for information written or printed there. In some situations, natural English might prefer:

• The number is in the form
• The number appears on the form
• The number is listed on the form

So the Serbian structure stays the same, but the best English wording can vary a little depending on context.