Ta kołysanka jest spokojna, więc dziecko szybko zasypia.

Ta means this and sometimes, depending on context, can feel close to that.

It is not a Polish word for the, because Polish does not have articles like English a and the. So:

• Kołysanka jest spokojna = The lullaby is calm / A lullaby is calm
• Ta kołysanka jest spokojna = This lullaby is calm

Adding ta makes the noun more specific.

Because ta has to match the grammatical gender of kołysanka.

In Polish, demonstratives change by gender:

• ten = masculine
• ta = feminine
• to = neuter

Kołysanka is a feminine noun, so the correct form is ta kołysanka.

A very common clue is the ending -a. Most Polish nouns ending in -a are feminine.

So:

• kołysanka = feminine
• therefore ta
• therefore spokojna

This is why both the demonstrative and the adjective use feminine forms.

Because adjectives must agree with the noun they describe.

Since kołysanka is:

• singular
• feminine
• nominative

the adjective must also be:

• singular
• feminine
• nominative

So you get spokojna.

Compare:

• spokojny chłopiec = a calm boy
• spokojna dziewczynka = a calm girl
• spokojne dziecko = a calm child

Because spokojna is an adjective, and spokojnie is an adverb.

Here the word describes the noun kołysanka, so you need an adjective:

• Ta kołysanka jest spokojna = The lullaby is calm

If you wanted to describe how someone sleeps or behaves, you would use the adverb:

• Dziecko śpi spokojnie = The child sleeps peacefully

So:

• spokojna = calm, peaceful as a quality of a noun
• spokojnie = calmly, peacefully as a manner

In a normal sentence like this, jest is needed.

Jest is the 3rd person singular present form of być = to be.

So:

• Ta kołysanka jest spokojna = This lullaby is calm

Unlike some other Slavic languages, standard Polish normally does not omit the present-tense form of to be in sentences like this.

You may sometimes see omissions in very informal speech, headlines, or stylized language, but for normal standard Polish, jest is the correct choice here.

Więc means so, therefore, or thus. It introduces a result.

In this sentence:

• Ta kołysanka jest spokojna, więc dziecko szybko zasypia.
• The lullaby is calm, so the child falls asleep quickly.

By contrast, bo means because and introduces a reason.

Compare:

• Dziecko szybko zasypia, bo kołysanka jest spokojna.
• The child falls asleep quickly because the lullaby is calm.

So the difference is:

• więc = result
• bo = cause

Because in Polish, więc is normally preceded by a comma when it links two clauses.

Here you have:

• Ta kołysanka jest spokojna
• dziecko szybko zasypia

These are two separate clauses, and więc connects them, so the comma is standard and expected.

This is a very common Polish punctuation pattern.

Because grammatical gender in Polish does not always match natural gender.

Dziecko is grammatically neuter, even though a child is of course a person. This is just how the noun works in Polish.

That means it takes neuter agreement:

• to dziecko = this child
• małe dziecko = a small child

In your sentence, you do not directly see adjective agreement with dziecko, but it is still a neuter noun.

No. Zasypia and śpi are different.

• zasypia = falls asleep, is falling asleep
• śpi = sleeps, is asleep

So zasypia focuses on the moment or process of going to sleep, not on the state after that.

In this sentence:

• dziecko szybko zasypia = the child falls asleep quickly

not

• the child sleeps quickly

Also, zasypia is from the imperfective verb zasypiać. A related perfective verb is zasnąć.

Very roughly:

• zasypiać = to be falling asleep / to fall asleep in a general or repeated sense
• zasnąć = to fall asleep once, as a completed event

Not necessarily. Polish present tense can describe:

• something happening now
• a repeated action
• a general truth or typical result

So dziecko szybko zasypia could mean:

• the child is falling asleep quickly right now, or
• the child usually falls asleep quickly when hearing this lullaby

Without more context, both are possible. In a sentence like this, many learners should read it as a natural general result: the lullaby is calm, so the child quickly falls asleep.

No, Polish word order is fairly flexible, but this version sounds neutral and natural.

• dziecko szybko zasypia = neutral
• dziecko zasypia szybko = also possible, with slightly different emphasis
• szybko zasypia dziecko = much more marked, often poetic or contrastive

English relies heavily on word order for grammar, but Polish uses endings much more, so word order is often used for focus and emphasis instead.

A few useful pronunciation points:

• kołysanka: stress on san → ko-ły-SAN-ka
• więc: one syllable
• dziecko: stress on the first syllable because it has only two syllables → DZIE-cko

Important sounds:

• ł sounds like English w
• y has no exact English equivalent; it is not the same as English ee
• ę in więc before c is often pronounced close to en
• dzie is a soft sound, somewhat like a very soft je with a d in front

Very rough learner-friendly approximations:

• kołysanka ≈ ko-wih-SAN-ka
• więc ≈ vyents
• dziecko ≈ dzhyets-ko

These are only approximations, but they help with the main difficult sounds.