Slon je danas bio miran i polako je hodao.

Because there are two past-tense verb forms in the sentence:

• je bio = was
• je hodao = was walking / walked

In Croatian, the past tense is usually made with:

• a form of biti (to be) in the present tense
• • the past active participle

So:

• je bio = he/it was
• je hodao = he/it walked / was walking

Even though English does not repeat was in the same way, Croatian normally does because each verb phrase needs its own auxiliary.

Both forms contain the same words, but Croatian has rules about clitics—short unstressed words like je.

The auxiliary je is a clitic, and clitics usually appear near the beginning of the clause, often in second position.

So Croatian prefers:

• Slon je danas bio miran
  rather than
• Slon bio je danas miran

That second version sounds unnatural in normal speech.

The same thing happens in:

• polako je hodao

The je comes early in its clause.

Bio is the masculine singular past participle of biti (to be).

It agrees with the subject:

• slon is a masculine singular noun
• so the participle is bio

Compare:

• slon je bio miran = the elephant was calm
• žirafa je bila mirna = the giraffe was calm
• dijete je bilo mirno = the child was calm

So bio changes depending on the gender and number of the subject.

Because miran is an adjective describing slon, and it must agree with the noun in gender, number, and case.

• slon = masculine singular
• so the adjective is miran

Other forms would be:

• mirna for feminine singular
• mirno for neuter singular
• mirni / mirne / mirna for plural, depending on gender and usage

Here:

• Slon je bio miran = masculine singular subject + masculine singular adjective

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

The basic dictionary form is:

• slon = elephant

Since the elephant is the one doing the action and being described, nominative is used:

• Slon je bio miran
• Slon je hodao

No case ending is added here because many masculine nouns have no ending in the nominative singular.

Croatian often omits subject pronouns when they are not needed.

In English, you usually need:

• He was calm and he walked slowly
• or It was calm and it walked slowly

In Croatian, the verb forms already help show what is going on, and the noun slon has already been stated, so repeating a pronoun is unnecessary.

That is why Croatian says:

• Slon je danas bio miran i polako je hodao

rather than something like:

• Slon je danas bio miran i on je polako hodao

Adding on is possible, but it usually adds emphasis or contrast.

It can mean either, depending on context.

Hodao is the past participle of hodati, an imperfective verb. Imperfective verbs often describe:

• an ongoing action
• a repeated action
• a general process

So je hodao can be understood as:

• walked
• was walking
• sometimes used to walk, depending on context

In this sentence, because of polako and the overall description, English often naturally uses was walking slowly, but walked slowly may also fit in some contexts.

Because the past participle in Croatian agrees with the subject, just like bio does.

The subject is:

• slon = masculine singular

So the participle is:

• hodao = masculine singular

Compare:

• Slon je hodao. = masculine singular
• Žirafa je hodala. = feminine singular
• Dijete je hodalo. = neuter singular

This agreement is a very important feature of the Croatian past tense.

Polako is an adverb, meaning something like slowly.

It modifies the verb:

• hodao = walked / was walking
• polako je hodao = walked slowly / was walking slowly

It does not change form, because adverbs do not agree with nouns the way adjectives do.

Compare:

• miran = adjective, describes slon
• polako = adverb, describes how he walked

Danas means today and acts as a time adverb.

In this sentence it tells us when the elephant was calm:

• Slon je danas bio miran...

Croatian word order is fairly flexible, so danas can move around, although some positions sound more natural than others.

For example:

• Slon je danas bio miran. = very natural
• Danas je slon bio miran. = also natural, with more focus on today
• Slon danas je bio miran. = possible, but less neutral

So word order can affect emphasis.

I simply means and.

It connects two ideas about the same subject:

• Slon je danas bio miran
• polako je hodao

So the full sentence means that both things were true:

1. the elephant was calm
2. the elephant walked slowly

Since the subject stays the same, Croatian does not need to repeat slon.

Croatian word order is more flexible than English, but not completely free.

The neutral version here is:

• Slon je danas bio miran i polako je hodao.

Other versions are possible for emphasis, for example:

• Danas je slon bio miran i polako je hodao.
  Focuses more on today.

• Slon je bio miran danas i polako je hodao.
  Possible, but less neutral in many contexts.

However, clitics like je still have placement rules, so you cannot move words completely freely.

The auxiliary je would stay the same for singular third person, but the participles and adjective would change to agree with the subject.

For a feminine singular subject:

• Žirafa je danas bila mirna i polako je hodala.

For a neuter singular subject:

• Dijete je danas bilo mirno i polako je hodalo.

For masculine plural:

• Slonovi su danas bili mirni i polako su hodali.

So in Croatian, agreement affects:

• the past participles
• the adjective
• and sometimes the auxiliary too, if number changes (je → su)

Yes. It sounds like a description of a situation rather than a single dramatic event.

That effect comes from several things:

• bio miran describes a state
• hodao is from an imperfective verb
• polako adds manner in a gentle, descriptive way
• danas places the scene in time

So the sentence feels like it is painting a picture:

• the elephant was calm today
• and it moved in a slow, steady way

That is why English might naturally translate it with was calm and was walking slowly, even though walked slowly can also work.