Ovaj san je bio lep.

• ovaj = this
• san = dream
• je = the present-tense form is
• bio = been/was in the masculine singular form
• lep = beautiful / nice / lovely

Grammatically, the sentence is built like this:

• Ovaj san = the subject, this dream
• je bio = the past-tense verb phrase, was
• lep = the description, beautiful/nice

So Serbian uses a form that literally looks like is been beautiful, but it means was beautiful.

Because san is a masculine singular noun, and ovaj must agree with it.

In Serbian, words like this change form depending on the gender of the noun:

• masculine: ovaj
• feminine: ova
• neuter: ovo

Since san is masculine, you say ovaj san.

You usually learn the noun’s gender together with the word. In this case, san is a masculine noun.

A useful clue is that many masculine nouns in Serbian end in a consonant, and san does. That pattern is very common, though not every noun can be guessed perfectly from the ending alone.

Because san is masculine, other words referring to it also appear in masculine forms:

• ovaj san
• san je bio
• san je bio lep

It is in the nominative singular.

That is the basic dictionary form, and it is used because san is the subject of the sentence: this dream was nice.

So:

• ovaj san = nominative singular masculine

If the noun had another role in the sentence, its form might change.

Because Serbian normally forms the past tense with:

• a present-tense form of biti (to be)
• plus the past participle

So here:

• je = present tense of to be
• bio = past participle, masculine singular

Together, je bio means was.

This is the standard Serbian perfect tense. English uses a simple past here, but Serbian often uses this compound form where English does not.

Because bio agrees with the subject, san, which is masculine singular.

The participle changes for gender and number:

• masculine singular: bio
• feminine singular: bila
• neuter singular: bilo
• plural masculine/mixed: bili
• plural feminine: bile
• plural neuter: bila

So:

• Ovaj san je bio lep. = masculine singular
• Ova priča je bila lepa. = feminine singular
• Ovo dete je bilo mirno. = neuter singular

For the same reason: lep agrees with san, which is masculine singular.

Adjectives in Serbian change to match the noun they describe:

• masculine singular: lep
• feminine singular: lepa
• neuter singular: lepo

So:

• lep san = a nice/beautiful dream
• lepa priča = a nice story
• lepo mesto = a beautiful place

In Ovaj san je bio lep, the adjective is used after the verb, but it still agrees with the subject.

Because here lep is an adjective, not an adverb.

The sentence describes the dream itself, not the manner of an action. So Serbian uses the adjective form:

• san je bio lep = the dream was beautiful

The form lepo can also be an adverb meaning beautifully / nicely, as in:

• Lepo peva. = She sings beautifully.

But in your sentence, the word describes a noun, so the masculine adjective lep is correct.

It can mean both, depending on context.

In a sentence about a dream, lep often means something like:

• beautiful
• lovely
• nice
• pleasant

So Ovaj san je bio lep could sound natural in English as:

• This dream was beautiful
• This dream was lovely
• This was a nice dream

The exact English choice depends on the tone.

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

The most neutral version is:

• Ovaj san je bio lep.

But other orders are possible for emphasis or style, for example:

• Ovaj san bio je lep.
• Lep je bio ovaj san.

These do not usually change the basic meaning, but they can change what is emphasized. English is much less flexible here, so learners often notice Serbian word order feels freer.

In standard modern Serbian, no: in an ordinary sentence like this, you normally keep je.

So the standard form is:

• Ovaj san je bio lep.

Without je, the sentence would sound incomplete or nonstandard in ordinary usage.

It actually can be.

• Ovaj san je bio lep. = neutral, ordinary word order
• Ovaj je san bio lep. = also correct, often with slight emphasis on this dream

Serbian clitics like je tend to go in second position, but what counts as the first element can vary depending on how the sentence is structured. So both versions are possible.

For a beginner, the safest default is:

• Ovaj san je bio lep.

A simple approximate pronunciation for an English speaker is:

OH-vai sahn yeh BEE-oh lep

A bit more carefully:

• ovaj ≈ OH-vai
• san ≈ sahn
• je ≈ yeh
• bio ≈ BEE-oh
• lep ≈ lep with a short e, not like English leep

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

Yes, it is a perfectly natural sentence.

A speaker might also say similar things like:

• San je bio lep. = The dream was nice.
• Bio je to lep san. = It was a beautiful dream.
• Ovo je bio lep san. = This was a beautiful dream.

Your sentence is clear, correct, and natural Serbian.