Izmjenjivač radi tiho.

Izmjenjivač is a noun. In this sentence, it is nominative singular, because it is the subject of the sentence.

It is also a masculine noun. You can often tell that from the consonant ending in the dictionary form.

So structurally:

• izmjenjivač = the subject
• radi = the verb
• tiho = an adverb describing how it works

Here, radi is the 3rd person singular present tense of raditi.

So:

• ja radim = I work / I am working
• ti radiš = you work
• on/ona/ono radi = he/she/it works

In this sentence, radi means something like:

• works
• operates
• is functioning

For a machine or device, radi is very natural Croatian.

Because tiho is an adverb, while tih is an adjective.

Here, the word describes how the exchanger works, not what kind of exchanger it is.

• tih izmjenjivač = a quiet exchanger
  
  • tih is an adjective modifying the noun
• izmjenjivač radi tiho = the exchanger works quietly
  
  • tiho is an adverb modifying the verb

This is very similar to English:

• quiet machine
• works quietly

The most neutral word order is:

• Izmjenjivač radi tiho.

But Croatian word order is more flexible than English. You may also hear different orders for emphasis, for example:

• Tiho radi izmjenjivač.
• Radi tiho izmjenjivač.

These are less neutral and would usually depend on context or emphasis.

For a learner, subject + verb + adverb is the safest and most natural pattern here.

Yes, very often.

Since the verb radi already shows 3rd person singular, Croatian can omit the subject if it is clear from context:

• Radi tiho. = It works quietly.

That said, keeping izmjenjivač in the sentence is perfectly normal when you want to state clearly what is being talked about.

Because Croatian does not have articles like a and the.

So izmjenjivač can mean, depending on context:

• an exchanger
• the exchanger

Context tells you which one is meant.

This is one of the big differences from English.

A rough pronunciation guide is:

• iz-mye-nyee-vach

A few useful points:

• j in Croatian is pronounced like English y in yes
• č sounds like ch in church, but usually a bit firmer/cleaner
• stress is not usually marked in normal writing, so learners often just imitate native audio at first

So izmjenjivač is approximately:

iz-mye-nyee-vach

Yes. This is a very good thing to notice.

Radi can also be a preposition meaning for the sake of or because of, used with the genitive, for example:

• radi sigurnosti = for safety / for the sake of safety

But in Izmjenjivač radi tiho, radi is clearly the verb works / operates, because:

• it comes right after the subject
• it matches the subject in person and number
• tiho naturally describes the verb

So here there is no ambiguity in practice.

Yes.

Croatian present tense often covers both:

• works
• is working

So Izmjenjivač radi tiho can mean either:

• The exchanger works quietly
  or
• The exchanger is working quietly

The exact meaning depends on context. Croatian does not usually make this distinction as strictly as English does.

The negative is:

• Izmjenjivač ne radi tiho.

Here:

• ne radi = does not work quietly / is not operating quietly

Croatian usually forms negation by putting ne before the verb.

Yes, absolutely.

It is a short, clear, natural sentence. It sounds like something you might read in:

• a technical description
• product documentation
• an inspection report
• a conversation about a device or machine

So as a model sentence for grammar and basic structure, it is completely normal.