Ona je zdrava, jer često jede voće i povrće.

Because ona means she, so the adjective has to match a feminine singular subject.

• zdrav = healthy, masculine
• zdrava = healthy, feminine
• zdravo = healthy, neuter

So:

• On je zdrav. = He is healthy.
• Ona je zdrava. = She is healthy.

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

So Ona je zdrava literally works like She is healthy.

Present tense of biti:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is
• mi smo = we are
• vi ste = you are
• oni/one/ona su = they are

Unlike Russian, Serbian normally does use the present tense of to be.

Jer means because.

It introduces the reason:

• Ona je zdrava, jer često jede voće i povrće.
• She is healthy, because she often eats fruit and vegetables.

A very common alternative is zato što, which also means because:

• Ona je zdrava zato što često jede voće i povrće.

Both are natural. Jer is short and very common.

In Serbian, a comma is normally used before jer when it introduces an explanatory clause.

So:

• Ona je zdrava, jer često jede voće i povrće.

This is standard punctuation in Serbian.

Često means often, and it is an adverb. In Serbian, adverbs commonly go before the verb, especially in neutral word order.

So:

• često jede = often eats

That is the most natural basic order here.

You may also see different word orders for emphasis, but često jede is the standard, neutral one.

Jede is the 3rd person singular present form of jesti (to eat), because the subject is ona (she).

Present tense of jesti:

• ja jedem = I eat
• ti jedeš = you eat
• on/ona/ono jede = he/she/it eats
• mi jedemo = we eat
• vi jedete = you eat
• oni/one/ona jedu = they eat

So:

• ona jede = she eats

They are in the accusative, because they are the direct objects of jede.

She eats what?

• voće
• povrće

However, for these neuter nouns, the accusative singular looks the same as the nominative singular.

So even though the case is accusative, the form does not change here.

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

So:

• voće can mean fruit, the fruit, or sometimes some fruit
• povrće can mean vegetables, the vegetables, or some vegetables

The exact meaning depends on context.

This is a very common adjustment for English speakers learning Serbian.

Yes. Serbian often drops subject pronouns because the verb form already shows the person.

So you can say:

• Je zdrava, jer često jede voće i povrće.

But in practice, that exact sentence sounds a bit incomplete at the beginning without context. More naturally, you might say:

• Zdrava je, jer često jede voće i povrće.

Or if the subject is already known:

• Često jede voće i povrće, pa je zdrava.

Using ona is fine when you want to be clear, contrast her with someone else, or make the subject explicit.

Yes. Serbian word order is more flexible than English, though some versions sound more neutral than others.

Neutral version:

• Ona je zdrava, jer često jede voće i povrće.

Other possible versions:

• Zdrava je, jer često jede voće i povrće.
• Jer često jede voće i povrće, ona je zdrava.
  This is grammatical, but less neutral and more stylistically marked.
• Ona često jede voće i povrće, pa je zdrava.

So the order can change, but the original sentence is a very natural standard pattern.

The main thing English speakers usually notice is the letter č.

• č is like ch in church, but usually a bit firmer
• ć is a softer sound than č, though many learners do not master the difference immediately

In this sentence:

• često = CHES-to
• voće = roughly VO-che
• povrće = roughly PO-vr-che

A few pronunciation notes:

• r in povrće is a trilled or tapped r
• Serbian spelling is very phonetic: words are usually pronounced much as they are written

Voće is usually treated as a collective/mass noun, similar to English fruit in a general sense.

So:

• jede voće = eats fruit

Likewise:

• povrće = vegetables / vegetable matter in a general sense

Even though English often uses a plural for vegetables, Serbian commonly uses the singular-looking mass noun povrće.

So the sentence sounds completely natural as written.

Yes, definitely.

These are both common:

• Ona je zdrava, jer često jede voće i povrće.
• Ona je zdrava zato što često jede voće i povrće.

A small practical difference:

• jer is shorter and very common in everyday speech
• zato što is also common and can feel a little more explicit

For a learner, both are worth knowing.