Kad šivaći stroj radi preglasno, ona poslije mora odmoriti ruke.

Kad means when here. It introduces a time clause: When the sewing machine works too loudly...

Yes, kad and kada usually mean the same thing in this kind of sentence. Kada is a little fuller/formal, while kad is very common in everyday speech and writing.

So these are both possible:

• Kad šivaći stroj radi preglasno...
• Kada šivaći stroj radi preglasno...

Šivaći means for sewing / sewing in the sense of describing the machine’s function. So šivaći stroj is a sewing machine.

It comes from the verb šivati = to sew, but here it behaves like an adjective modifying stroj.

A useful comparison:

• šivati = to sew
• šivaći stroj = sewing machine

So this is not saying the machine is literally sewing right now as an adjective like English sewing sometimes can. It is simply the established name of the object.

It is in the nominative singular because it is the subject of the verb radi.

Breakdown:

• šivaći stroj = the sewing machine
• radi = works / operates

So the structure is:

• [Subject] šivaći stroj
• [Verb] radi

Here radi means works, operates, or is running.

The verb raditi can mean several things depending on context:

• to work (as in to have a job)
• to function / operate
• sometimes to do / make

In this sentence, because the subject is šivaći stroj (a machine), radi clearly means is operating / is running.

So:

• Stroj radi. = The machine is working / running.

Preglasno means too loudly.

It is built from:

• glasan = loud
• glasno = loudly
• pre- = too, excessively

So:

• glasno = loudly
• preglasno = too loudly / excessively loudly

This prefix pre- is very common in Croatian:

• prebrzo = too fast
• previše = too much
• prevruće = too hot

Because Kad šivaći stroj radi preglasno is a subordinate clause placed before the main clause.

Croatian normally separates this kind of introductory clause with a comma:

• Kad šivaći stroj radi preglasno, ona poslije mora odmoriti ruke.

This is similar to English:

• When the sewing machine runs too loudly, she later has to rest her hands.

If the main clause came first, the comma usage would depend on the structure, but with this fronted kad clause, the comma is standard.

Yes, Croatian could leave it out.

Because the verb form already shows the person, Croatian often drops subject pronouns when they are not needed. So this sentence could also be:

• Kad šivaći stroj radi preglasno, poslije mora odmoriti ruke.

That still means When the sewing machine is too loud, she later has to rest her hands.

Including ona can add:

• emphasis
• contrast
• clarity about who is being talked about

So ona is not wrong at all; it is just more explicit than Croatian strictly requires.

Yes, poslije here means afterwards, later, or then depending on context.

In this sentence it means that after the sewing machine has been running too loudly, she later has to rest her hands.

Common equivalents:

• poslije = later / afterwards
• sometimes after in other contexts

A close alternative is kasnije:

• ona poslije mora odmoriti ruke
• ona kasnije mora odmoriti ruke

Both are possible, though poslije often feels very natural in everyday speech.

This is because morati means must / have to, and it is followed by an infinitive.

So:

• mora = must / has to
• odmoriti = to rest

Together:

• mora odmoriti ruke = has to rest her hands

This is the same pattern you see in many Croatian sentences:

• Mora ići. = She has to go.
• Mora raditi. = She has to work.
• Mora odmoriti ruke. = She has to rest her hands.

Yes. Croatian can use odmoriti transitively, meaning to rest some body part or person.

So:

• odmoriti ruke = to rest one’s hands

This is natural Croatian. English often uses a possessive:

• rest her hands

Croatian does not need to say njezine ruke here, because the meaning is clear from context.

Compare:

• Mora odmoriti ruke. = She has to rest her hands.
• Mora se odmoriti. = She has to rest / She has to take a rest.

Those are different:

• odmoriti ruke = rest the hands
• odmoriti se = rest oneself

This is about aspect.

• odmoriti is perfective
• odmarati is imperfective

With morati, Croatian often uses the perfective infinitive when talking about a needed completed action:

• mora odmoriti ruke = she needs to rest her hands (as a complete act)

If you used odmarati, it would suggest a more ongoing or repeated process:

• mora odmarati ruke = she has to be resting her hands / has to rest her hands regularly

In this sentence, odmoriti fits better because it refers to the necessary act of giving the hands rest.

Ruke is the accusative plural here, because it is the direct object of odmoriti.

The basic noun is:

• ruka = hand / arm

Forms:

• ruka = nominative singular
• ruke = nominative plural or genitive singular
• ruke = accusative plural in this sentence

Why accusative plural here? Because she is resting her hands — the thing being rested is the direct object.

Because Croatian often leaves possession understood when it is obvious, especially with body parts.

So:

• odmoriti ruke naturally means rest her hands here

If you said odmoriti svoje ruke or odmoriti njezine ruke, it would be more explicit, but usually unnecessary.

This is very common with body parts in Croatian:

• Operi ruke. = Wash your hands.
• Boli me glava. = My head hurts. / I have a headache.
• Zatvorio je oči. = He closed his eyes.

Croatian often relies on context instead of possessive adjectives in these cases.

Yes, Croatian word order is fairly flexible, but not every order sounds equally natural.

The given sentence is natural:

• Kad šivaći stroj radi preglasno, ona poslije mora odmoriti ruke.

You could also say:

• Kad šivaći stroj radi preglasno, poslije mora odmoriti ruke.
• Ona mora poslije odmoriti ruke kad šivaći stroj radi preglasno.

But changing the order can change:

• what gets emphasis
• what sounds most natural
• how easy the sentence is to process

The original version is a good neutral model for learners.

It can most naturally be understood as a general or repeated situation:

• Whenever/when the sewing machine runs too loudly, she later has to rest her hands.

Croatian present tense often does this, especially with kad clauses. It does not have to mean only right now.

So the sentence can describe:

• a usual consequence
• a repeated experience
• a general fact in a story or explanation

Context would decide whether it means whenever this happens or when this happens in the situation we are discussing.