Learn Hardcore Croatian: Šetalište je mirno kad nema puno ljudi i svi tiho razgovaraju. - The promenade is calm when there are not many people and everyone talks quietly.

Šetalište is usually translated as promenade, walkway, or esplanade – a place meant for walking, often by the sea, a river, or through a park.

A few details:

It’s a neuter noun (nominative singular): to šetalište.
It comes from the verb šetati (to walk, to stroll).
It is not a general word for street (that’s ulica).
So:
- ulica = street (with cars, buildings, etc.)
- šetalište = pedestrian path / promenade, for walking

Why is it mirno and not miran or mirna?

The form of the adjective must agree with the gender and number of the noun šetalište.

Šetalište is neuter singular.
The base adjective is miran (quiet, peaceful).
Its neuter singular form is mirno.

So:

miran – masculine (e.g. miran čovjek – a quiet man)
mirna – feminine (e.g. mirna ulica – a quiet street)
mirno – neuter (e.g. mirno šetalište – a quiet promenade)

In the sentence, mirno is used as a predicative adjective after je:

Šetalište je mirno.
The promenade is quiet.
(literally: The promenade is quiet-neuter.)

What is the difference between kad and kada?

Both kad and kada mean when and introduce a time clause.

kada – full form, a bit more formal or neutral in writing.
kad – shortened, more common in everyday speech and informal writing.

You can normally replace one with the other without changing the meaning:

Šetalište je mirno kad nema puno ljudi.
Šetalište je mirno kada nema puno ljudi.

Both mean: The promenade is quiet when there aren’t many people.

How does the phrase nema puno ljudi work grammatically?

Nema puno ljudi literally corresponds to there isn’t / there aren’t many people.

Breakdown:

nema = ne
- ima
  - ima = there is / there are (literally: has)
  - nema = there is not / there are not
puno = a lot (of), much, many
ljudi = genitive plural of ljudi (people)

In Croatian, after quantity words like puno, you normally use the genitive:

puno ljudi – a lot of people
puno vremena – a lot of time

So:

nema puno ljudi = there aren’t many people / there are not a lot of people
(literally: is-not a-lot of-people)

Why is the word ljudi used here, and what form is it?

Ljudi means people and here it is in the genitive plural.

It’s a bit special:

Singular: čovjek – a person / a man
Plural (nominative): ljudi – people
Genitive plural: ljudi – of people (same form)

So the phrase puno ljudi uses genitive plural, required by puno.
You do not say puno ljudi in nominative; the form just happens to look the same.

Can I say mnogo instead of puno, or use osoba instead of ljudi?

Yes, these are possible, but they differ slightly in style and nuance:

puno ljudi – very common, everyday speech, neutral.
mnogo ljudi – a bit more formal, typical in more careful or written language.
puno / mnogo osoba – osoba = person (counting individuals, more formal/technical).

In your sentence:

kad nema puno ljudi – the most natural, conversational option.
kad nema mnogo ljudi – also correct, slightly more formal.
kad nema puno osoba – grammatically correct, but would sound more like you are counting individuals in a formal context (e.g. safety regulations) rather than describing a relaxed, general situation.

For a normal description of a quiet promenade, puno ljudi is the best.

Why is there no comma before kad in the sentence?

Many native speakers often omit the comma in short everyday sentences like this, especially in informal writing:

Šetalište je mirno kad nema puno ljudi...

In more formal written Croatian, you will often see a comma before a subordinate clause introduced by kad / kada:

Šetalište je mirno, kad nema puno ljudi i svi tiho razgovaraju.

So:

Without comma: common in informal texts, still widely accepted.
With comma: more in line with traditional school grammar, especially in formal writing.

For learning purposes, it’s safe (and stylistically good) to put the comma before kad when it starts a subordinate clause after the main clause.

Why is it tiho and not tihi or tiha?

In svi tiho razgovaraju, tiho is an adverb: quietly / softly.

The adjective is tih (quiet).
Its adverb form is tiho (quietly).

When you modify a verb like razgovarati (to talk), you need an adverb, not an adjective:

Svi tiho razgovaraju. – Everyone talks quietly.
Not: Svi tihi razgovaraju.
That would mean: All (those who are) quiet talk, which is a different structure.

So:

tih / tiha / tiho – adjective forms (quiet)
tiho – adverb (quietly)

Can I change the word order, like Svi razgovaraju tiho or move the kad clause?

Yes, Croatian word order is fairly flexible, and these alternatives are natural:

Svi tiho razgovaraju.
Svi razgovaraju tiho.

Both mean Everyone is talking quietly, with a slight difference in emphasis:

Svi tiho razgovaraju – more emphasis on how they talk (quietly).
Svi razgovaraju tiho – a bit more neutral.

You can also move the kad clause to the beginning:

Kad nema puno ljudi i svi tiho razgovaraju, šetalište je mirno.
When there aren’t many people and everyone talks quietly, the promenade is quiet.

This version is very natural in Croatian and is sometimes even preferred for clarity.

Why is the present tense used here? Could I use another tense?

The present tense in Croatian is used both for:

Current actions – what is happening now.
General truths / habitual situations – what typically happens.

Your sentence describes a general, habitual situation:

Šetalište je mirno kad nema puno ljudi i svi tiho razgovaraju.
The promenade is (generally) quiet when there aren’t many people and everyone speaks quietly.

So the present tense is exactly what you want here.
Other tenses (like past or future) would change the meaning to a specific past/future situation.

What does svi mean here, and how is it different from sve?

Svi means all / everyone and is used with masculine or mixed-gender groups.

svi – masculine (or mixed) plural nominative
sve – feminine plural nominative, or neutral plural in some uses

In the sentence:

svi tiho razgovaraju = everyone talks quietly.

You use svi because you are referring to people in general, which in Croatian grammar is treated as masculine plural (or mixed).

Examples:

Svi su došli. – Everyone came.
Sve su došle. – All of them (all women) came.

What cases are used for the main nouns in this sentence?

The key nouns and their cases:

Šetalište – nominative singular neuter (subject of je mirno)
ljudi – genitive plural (after quantity word puno)

Verbs:

je – 3rd person singular present of biti (to be)
nema – 3rd person singular present of imati with negation (ne + ima → nema)
razgovaraju – 3rd person plural present of razgovarati (they talk / converse)

Pronoun:

svi – nominative plural (subject of razgovaraju)

So the structure is:

Šetalište (NOM) je mirno (predicate)
kad nema puno ljudi (GEN after puno)
i svi (NOM) tiho razgovaraju (verb + adverb).