Nažalost, jedan gost je rekao da neće doći, jer mu je dijete bolesno.

Yes, jedan literally means one, but in Croatian it can also work like an indefinite article in contexts where English would say a or an.

So:

• jedan gost = one guest or a guest
• In this sentence, it most naturally means a guest

Croatian has no articles, so words like jedan are sometimes used when the speaker wants to introduce someone as one / a certain person.

You could also hear:

• Gost je rekao... = A/The guest said...

That is normal too. Adding jedan just makes the person feel a little more newly introduced or singled out.

Both are possible in Croatian.

• jedan gost je rekao
• jedan gost rekao je

Both mean the same thing: a guest said

The auxiliary verb je often appears in the second position of the clause. This is a common Croatian word-order pattern for short unstressed words called clitics.

In this sentence:

• jedan gost is treated as the first unit
• so je comes after it

That gives:

• Jedan gost je rekao...

You may also see different word orders for emphasis or style, but this version is very standard and natural.

After verbs like reći (to say), Croatian often uses da to introduce a subordinate clause.

So:

• rekao je da... = he said that...

In your sentence:

• rekao da neće doći = said that he wouldn’t come

This is very common Croatian structure:

• Mislim da... = I think that...
• Znam da... = I know that...
• Rekao je da... = He said that...

English can sometimes drop that, but Croatian usually keeps da in this kind of sentence.

Neće doći is the future tense in the negative.

It comes from:

• htjeti = to want, but it is also used to form the future
• će = future auxiliary
• doći = to come

Positive future:

• doći će = he/she will come

Negative future:

• neće doći = he/she will not come

A very important point:

• in the positive, the clitic auxiliary often comes after the verb: doći će
• in the negative, neće is written as one word and comes before the infinitive: neće doći

So:

• doći će = will come
• neće doći = will not come

Doći is the infinitive of the verb to come.

It is an important irregular verb. Its forms are based on different stems, which is very common in Croatian motion verbs.

Some useful forms:

• doći = to come
• došao / došla = came
• dolazi = comes / is coming
• dođe = comes / may come, depending on context

So in this sentence:

• neće doći = will not come

You should simply learn doći as the infinitive form used after the future auxiliary.

Because jer introduces a subordinate clause meaning because.

So the sentence is divided into:

• Nažalost, jedan gost je rekao da neće doći,
• jer mu je dijete bolesno.

This is similar to English punctuation, where a clause introduced by because may also be separated depending on sentence structure and style. In Croatian, commas before conjunctions introducing subordinate clauses are common and standard.

Both can mean because.

• jer = because
• zato što = because

In many situations, they are interchangeable:

• Neće doći jer mu je dijete bolesno.
• Neće doći zato što mu je dijete bolesno.

Both mean: He won’t come because his child is ill.

A rough difference:

• jer is short, neutral, and very common
• zato što can sound a little more explicit or emphatic

For this sentence, jer is perfectly natural.

Mu means to him or his, depending on how you translate it naturally into English.

It is the dative singular clitic pronoun of on (he).

Here:

• mu je dijete bolesno

literally means something like:

• to him the child is ill

But natural English is:

• his child is ill
• or his child is sick

Croatian often uses a dative pronoun where English uses a possessive adjective.

Compare:

• Boli me glava. = My head hurts.
  literally: The head hurts to me.
• Mu je dijete bolesno. = His child is ill.

So mu refers back to the guest.

Both are possible, but the sentence uses a very common clitic order.

Mu and je are unstressed short words, and Croatian usually places such clitics near the beginning of the clause.

So:

• jer mu je dijete bolesno = very natural, neutral
• jer dijete mu je bolesno = possible in some contexts, but less neutral and often less preferred
• jer je njegovo dijete bolesno = more explicit, more stressed

The pattern mu je is especially common.

Because dijete is a neuter noun in Croatian.

So the adjective must agree with it in gender, number, and case.

• masculine: bolestan
• feminine: bolesna
• neuter: bolesno

Since dijete is neuter singular, you need:

• dijete je bolesno

This is one of the important things learners must remember: grammatical gender does not always match natural gender.

Dijete is singular and means child.

It is a neuter noun, and its plural is irregular:

• singular: dijete = child
• plural: djeca = children

This pair is worth memorizing because it does not form the plural in the regular way.

So in your sentence:

• mu je dijete bolesno = his child is ill

That depends on the standard variety.

• dijete is standard Croatian
• dete is associated with Serbian or with nonstandard pronunciation/spelling from a Croatian perspective

If you are learning standard Croatian, use:

• dijete

This is part of the ije/je pattern common in Croatian spelling.

Nažalost means unfortunately.

It comments on the whole sentence, not just one word. It tells you the speaker views the situation as regrettable.

So:

• Nažalost, jedan gost je rekao...
  = Unfortunately, a guest said...

It is common to put a comma after Nažalost because it functions as a sentence adverb.

Other similar words are:

• Srećom = luckily
• Naravno = of course
• Vjerojatno = probably

Because Croatian has no definite or indefinite articles.

English distinguishes:

• a guest
• the guest

Croatian usually leaves that to context:

• gost can mean a guest or the guest
• jedan gost helps make it more like a guest / one guest

So learners coming from English need to get used to the fact that Croatian normally does not mark a/an/the at all.

Yes, in natural English that is a perfectly reasonable translation.

Croatian neće doći is literally will not come, but in context English often prefers:

• said he won’t come
• said he isn’t coming

Both can work depending on style and context.

The Croatian future here simply expresses a future event from the speaker’s perspective.

A rough guide:

• neće ≈ NEH-cheh
• dijete ≈ DYEH-teh or dee-YEH-teh, depending on how carefully you break it down

A few points:

• ć is a soft ch-like sound
• je / ije combinations can be tricky for English speakers
• Croatian pronunciation is usually quite phonetic, so spelling helps a lot

If you are learning standard Croatian, it is worth listening carefully to native audio for words like:

• neće
• doći
• dijete

because they contain sounds and combinations that English does not match exactly.

Yes. Bolesan / bolesna / bolesno can often be translated as either ill or sick.

So:

• dijete je bolesno = the child is ill
• dijete je bolesno = the child is sick

In everyday English, sick is often more common, while ill can sound slightly more formal in some contexts. Croatian bolesno covers both well here.