Bivši vođa zna tu činjenicu.

Because not all masculine nouns in Croatian have the endings English speakers expect.

Vođa is one of the nouns that can refer to a male person even though it ends in -a. In this sentence, it is clearly masculine because of bivši:

• bivši vođa = masculine
• bivša vođa = feminine

So the adjective tells you the gender here.

Bivši means former or ex-.

It describes someone who used to have a role, position, or status but does not have it now.

So:

• bivši vođa = former leader
• bivši muž = ex-husband
• bivša predsjednica = former president (female)

In this sentence, bivši is an adjective modifying vođa, and it agrees with it in gender, number, and case.

Because tu činjenicu is the direct object of the verb zna.

The dictionary form is:

• ta činjenica = that fact (nominative)

But after a transitive verb like znati (to know), the direct object normally goes into the accusative case:

• nominative: ta činjenica
• accusative: tu činjenicu

So:

• zna tu činjenicu = knows that fact

Both words change to match the accusative feminine singular form.

It is accusative singular feminine.

You can recognize it like this:

• činjenica → činjenicu
• ta → tu

That pattern is very common for many feminine nouns ending in -a:

• nominative: dobra knjiga
• accusative: dobru knjigu

So here:

• nominative: ta činjenica
• accusative: tu činjenicu

The accusative is used because činjenicu is what is being known.

In Croatian, znati is used for knowing facts, information, answers, skills, or truths.

So you say:

• Znam odgovor. = I know the answer.
• Zna tu činjenicu. = He/She knows that fact.

By contrast, poznavati / poznati is used more for being acquainted with people, places, or things:

• Poznajem Marka. = I know Mark.
• Dobro poznaje grad. = He/She knows the city well.

So with fact, znati is the natural choice.

Croatian normally does not use articles like the or a/an.

So a noun like vođa can mean:

• leader
• the leader
• a leader

The exact meaning depends on context.

In this sentence:

• bivši vođa can be understood as the former leader or a former leader, depending on context.
• tu činjenicu is more clearly specific because tu means that.

English needs articles, but Croatian usually does not.

No, Croatian word order is fairly flexible.

This sentence uses a very neutral, standard order:

• Bivši vođa = subject
• zna = verb
• tu činjenicu = object

But other orders are possible for emphasis, for example:

• Tu činjenicu zna bivši vođa.
  Emphasis on that fact
• Zna tu činjenicu bivši vođa.
  Less neutral, more marked

The original sentence is the most straightforward and natural choice for a learner.

A few sounds here are especially important:

• č = like ch in church, but usually a bit harder/crisper
• đ = similar to the j in jam, but softer

So roughly:

• vođa ≈ VO-ja
• činjenicu ≈ CHIN-ye-nee-tsu

A few details:

• j is pronounced like English y
• c is pronounced ts
• nj is like the ny sound in canyon

So činjenicu breaks down approximately as:

• či-nje-ni-cu

Yes, that is grammatically possible, but it changes the feel slightly.

• Bivši vođa zna tu činjenicu. = The former leader knows that fact.
• Bivši vođa zna činjenicu. = The former leader knows a/the fact depending on context, but it sounds less specifically pointed out.

Using tu makes the fact more specific and identifiable in the conversation, like English that fact.

Yes. Croatian adjectives agree with the noun they describe in:

• gender
• number
• case

Here, vođa is singular, nominative, and masculine, so the adjective is:

• bivši

If the noun were feminine, you would change it:

• bivša vođa

If it were plural, it would change again depending on gender and case.

Agreement is one of the key patterns to watch for in Croatian sentences.