Kad šivaći stroj ne radi, krojačica pegla košulje.

Both kad and kada mean when.

• kad is the shorter, very common everyday form.
• kada is a bit fuller and can sound slightly more formal or careful.

In this sentence, kad is completely natural: Kad šivaći stroj ne radi, krojačica pegla košulje.

Here ne radi means doesn’t work or is not working.

The verb raditi literally means to work, but with machines it often means to function / to operate.

So:

• Stroj radi = The machine works / is working
• Stroj ne radi = The machine doesn’t work / isn’t working

Croatian present tense often covers both the English simple present and present progressive.

So pegla can mean:

• irons
• is ironing

The exact meaning depends on context.

In this sentence, the meaning is probably something like when the sewing machine isn’t working, the seamstress irons shirts, which can sound habitual or situational.

It is basically when, but in real usage it can also feel like whenever in repeated situations.

So this sentence can be understood as:

• When the sewing machine doesn’t work, the seamstress irons shirts
• or Whenever the sewing machine isn’t working, the seamstress irons shirts

English may sometimes use if, but Croatian kad still literally means when.

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

It is the person doing the action:

• krojačica = the seamstress
• pegla = irons

So krojačica pegla = the seamstress irons

In this sentence, košulje is accusative plural because it is the direct object of pegla.

The seamstress is ironing shirts, so shirts are the thing affected by the action.

For many feminine nouns like košulja:

• nominative singular: košulja
• accusative singular: košulju
• nominative plural: košulje
• accusative plural: košulje

So yes, košulje looks the same in both nominative plural and accusative plural.

Šivaći is an adjective meaning sewing in the phrase šivaći stroj = sewing machine.

It is related to the verb šivati = to sew.

So:

• stroj = machine
• šivaći stroj = sewing machine

The adjective agrees with stroj, which is masculine singular, so the form is šivaći.

Because šivaći and šivajući are different forms with different jobs.

• šivaći is an adjective meaning sewing
• šivajući means something like sewing / while sewing, a participial form

For the name of the object, Croatian uses šivaći stroj, not šivajući stroj.

So think of šivaći stroj as a fixed expression meaning sewing machine.

The comma separates the subordinate clause from the main clause.

• Kad šivaći stroj ne radi = subordinate clause
• krojačica pegla košulje = main clause

Croatian normally uses a comma with clauses introduced by kad in sentences like this, especially when that clause comes first.

Yes. Croatian word order is more flexible than English because case endings help show grammatical roles.

For example, you could also say:

Krojačica pegla košulje kad šivaći stroj ne radi.

That still means the same thing.

The original order puts the when-clause first, which sounds natural if you want to set the situation first: When the sewing machine doesn’t work, ...

Croatian does not have articles like English the and a/an.

So:

• krojačica can mean a seamstress or the seamstress
• šivaći stroj can mean a sewing machine or the sewing machine
• košulje can mean shirts, the shirts, or sometimes some shirts

The context tells you which meaning is intended.

Yes, both are imperfective forms here, and that fits the meaning well.

• raditi is imperfective
• peglati is imperfective

Imperfective verbs are commonly used for:

• ongoing actions
• repeated actions
• general situations

That is why they work naturally in a sentence like this, which describes a situation or routine: When the sewing machine isn’t working, the seamstress irons shirts.

A few sounds may stand out to an English speaker:

• š = like sh in shoe
• č = like ch in church, usually a bit firmer
• ć = also similar to ch, but softer than č

So roughly:

• šivaći ≈ shee-vah-chee
• krojačica ≈ kroyah-chee-tsa
• košulje ≈ ko-shoo-lyeh

These are only rough English-style approximations, but they help get started.

Yes. Krojačica is a feminine noun and refers to a woman in that role, often translated as seamstress or female tailor.

The masculine form is krojač.

So:

• krojač = male tailor
• krojačica = female tailor / seamstress

In this sentence, the feminine noun is important because it tells you the subject is female.