Most je blizu reke.

Because blizu requires the genitive case.

The base form of river is reka. But after blizu (near), Serbian normally uses the genitive:

• reka = river
• reke = of the river / river in the genitive

So:

• blizu reke = near the river

This is one of those patterns you simply learn with the word blizu.

Most is in the nominative singular because it is the subject of the sentence.

In Most je blizu reke:

• Most = the bridge
• je = is
• blizu reke = near the river

Since the bridge is the thing being talked about, it stays in the nominative.

Je is the 3rd person singular present form of biti (to be).

So it means is.

The verb biti in the present tense is:

• sam = I am
• si = you are
• je = he/she/it is
• smo = we are
• ste = you are
• su = they are

In this sentence, most is singular, so Serbian uses je.

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

So most can mean:

• a bridge
• the bridge

Which one is intended depends on context.

That is why Most je blizu reke can be understood as The bridge is near the river or A bridge is near the river, depending on the situation.

In beginner learning, it is often easiest to think of blizu as a word meaning near/close to that is followed by the genitive.

In actual grammar descriptions, blizu is often treated as an adverb or a predicative word that can govern the genitive.

What matters most for a learner is this pattern:

• blizu + genitive

Examples:

• blizu kuće = near the house
• blizu škole = near the school
• blizu reke = near the river

Yes. Serbian word order is more flexible than English word order.

The neutral order here is:

• Most je blizu reke.

But other orders are possible, for example:

• Blizu reke je most.
• Most je reke blizu. — possible in poetry or marked style, but not the normal beginner pattern

Changing the order usually changes the focus or emphasis, not the basic meaning.

• most is masculine
• reka is feminine

You can see that in their dictionary forms:

• most = bridge, masculine noun
• reka = river, feminine noun

In the sentence:

• most stays nominative singular masculine
• reke is the genitive singular of feminine reka

No. Blizu does not change form here.

Unlike many Serbian adjectives, blizu stays the same:

• Most je blizu reke.
• Kuća je blizu reke.
• Mostovi su blizu reke.

What changes is usually the noun after it, because that noun goes into the genitive.

A simple learner-friendly pronunciation is:

most yeh BLI-zoo REH-keh

Roughly:

• most = like English most, but with a clear short o
• je = yeh
• blizu = BLI-zoo
• reke = REH-keh

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

No, that is not natural Serbian.

English uses near the river, and learners sometimes expect an extra word like of/from. But Serbian simply says:

• blizu reke

So the correct pattern is:

• blizu + genitive

not:

• blizu od + noun

The dictionary forms are:

• most = bridge
• biti = to be
• blizu = near / close
• reka = river

In the sentence, only reka changes form:

• dictionary form: reka
• sentence form: reke

That change happens because of the genitive after blizu.

Yes, absolutely.

Most je blizu reke. is a normal, complete sentence. It has:

• a subject: Most
• a verb: je
• a location expression: blizu reke

It sounds natural and grammatical in standard Serbian.