Z początku dzieci były ciche, ale potem zaczęły się śmiać.

Z początku means at first or initially.

It is very close in meaning to na początku, but there is a slight difference in feel:

• z początku = at first / initially
• na początku = at the beginning

In many sentences, both are possible, but z początku often sounds a bit more like you are describing an initial state that later changed, which fits this sentence very well:

• Z początku dzieci były ciche, ale potem... = At first the children were quiet, but then...

So yes, they are similar, but z początku is especially natural when contrasting the beginning with what happened later.

Because dzieci takes non-masculine-personal plural agreement in Polish grammar.

In the past tense, plural forms differ:

• byli = masculine personal plural
• były = non-masculine-personal plural

Even though children can include boys, grammatically dzieci behaves like a non-masculine-personal plural noun, so you say:

• dzieci były
• dzieci zaczęły

not:

• dzieci byli
• dzieci zaczęli

This is something learners often have to memorize: grammatical agreement does not always match natural gender in the way English speakers expect.

Ciche is the plural nominative form of the adjective cichy.

Because it describes dzieci, it has to agree with that noun in:

• number: plural
• gender type: non-masculine-personal
• case: nominative, because it is part of the predicate with być

So:

• singular: dziecko było ciche = the child was quiet
• plural: dzieci były ciche = the children were quiet

Because ciche is an adjective, while cicho is usually an adverb or predicative form.

Here, the sentence says that the children were quiet, so Polish uses an adjective agreeing with dzieci:

• dzieci były ciche

Compare:

• Dzieci były ciche. = The children were quiet.
• Było cicho. = It was quiet.

So:

• ciche describes the children
• cicho describes the general atmosphere or sound level

This is a very common Polish structure.

• zaczęły = they began / started
• śmiać się = to laugh

So literally it is:

• they started to laugh

Polish often uses:

• a conjugated verb like zacząć
• plus an infinitive like śmiać się

That is why you see both:

• zaczęły się śmiać = they started laughing / they began to laugh

Because śmiać się is the normal dictionary form of the verb meaning to laugh.

In Polish, some verbs naturally come with się. This does not always mean true reflexive action in the English sense. In this case, śmiać się simply means to laugh.

So you must say:

• śmiać się = to laugh
• dzieci śmiały się = the children were laughing
• dzieci zaczęły się śmiać = the children started laughing

You cannot normally drop się here.

In Polish, się is quite mobile, but some positions are more natural than others.

In this sentence:

• zaczęły się śmiać

the placement is very natural and standard.

You may also hear or see:

• zaczęły śmiać się

but that often sounds less neutral in everyday usage.

For learners, the safest pattern is:

• zacząć + się + infinitive
• zaczęły się śmiać
• zaczął się śmiać
• zaczęłam się śmiać

So the position of się here is something worth learning as a common pattern.

Because zacząć is perfective, and here it expresses a completed change of state: the children moved from being quiet to beginning to laugh.

• zaczęły się śmiać = they started laughing as a single event/change

If you used zaczynały, that would be the imperfective verb zaczynać, which usually suggests repeated action, background description, or an incomplete process in the past.

In this sentence, the perfective form is the natural choice because the speaker is narrating a clear sequence:

1. At first they were quiet
2. Then they started laughing

Ale means but, and potem means then / afterwards / later.

Together they create a strong contrast:

• Z początku dzieci były ciche = At first the children were quiet
• ale potem zaczęły się śmiać = but then they started laughing

So the sentence is built around a contrast between the initial situation and the later development.

Yes. Polish word order is more flexible than English word order, although some versions sound more natural than others.

The original sentence is very natural:

• Z początku dzieci były ciche, ale potem zaczęły się śmiać.

Possible variations include:

• Dzieci były z początku ciche, ale potem zaczęły się śmiać.
• Potem dzieci zaczęły się śmiać.

But the original order is especially good because it clearly sets up the timeline:

• z początku = first
• potem = later

So while other word orders are possible, this one is a very natural neutral choice.

Yes. Cichy / ciche can cover both ideas depending on context.

In this sentence, ciche most naturally means:

• quiet
• not making much noise

It does not necessarily mean complete silence; it just suggests that the children were calm or not noisy at first.

So a good understanding here is:

• At first the children were quiet, but then they started laughing.

With dziecko (child), the sentence would be:

• Z początku dziecko było ciche, ale potem zaczęło się śmiać.

Notice the agreement changes:

• dziecko → singular
• było instead of były
• ciche stays ciche here because it is the neuter singular form
• zaczęło instead of zaczęły

This is a useful comparison:

• dziecko było ciche = singular
• dzieci były ciche = plural

Yes, it is completely natural.

It sounds like normal, standard Polish and would work well in:

• conversation
• storytelling
• writing
• describing children’s behavior

It has a very natural rhythm:

• Z początku...
• ale potem...

That makes it a good model sentence for learning how Polish expresses contrast over time.