Zvono je toliko glasno da probudi bebu.

Because zvono is a neuter singular noun, and the predicate adjective has to match it.

• glasan = masculine singular
• glasna = feminine singular
• glasno = neuter singular

So:

• On je glasan. = He/It is loud.
• Ona je glasna. = She/It is loud.
• Zvono je glasno. = The bell is loud.

Here glasno is an adjective agreeing with zvono, not an adverb.

This is a very common Croatian pattern meaning so ... that ...

So:

• toliko glasno = so loud
• da probudi bebu = that it wakes the baby

The whole structure is:

• toliko + adjective/adverb + da + clause

Examples:

• Bio je toliko umoran da je odmah zaspao. = He was so tired that he fell asleep immediately.
• Auto je išao toliko brzo da ga nisam vidio. = The car was going so fast that I didn’t see it.

Here da introduces the second part of the sentence: the result clause.

In English, this is usually translated as that in a structure like so ... that ...

• Zvono je toliko glasno da probudi bebu.
• The bell is so loud that it wakes/will wake the baby.

So in this sentence, da is not meaning yes; it is a conjunction linking the result to the first clause.

Probudi is the 3rd person singular present form of the verb probuditi.

• infinitive: probuditi = to wake up, to awaken
• present:
  • ja probudim
  • ti probudiš
  • on/ona/ono probudi

Since the subject is zvono = the bell (a singular thing), Croatian uses probudi.

So literally:

• zvono ... probudi bebu = the bell wakes the baby

This is about aspect, which is very important in Croatian.

• buditi = imperfective, focusing on the process or repeated action
• probuditi = perfective, focusing on the completed result: someone ends up awake

In this sentence, the idea is the result of the loud bell: it is loud enough to wake the baby up. That is why probuditi fits well.

So:

• buditi bebu = to be waking the baby / to wake the baby repeatedly
• probuditi bebu = to wake the baby up successfully

With toliko ... da ..., Croatian often uses a perfective verb to show the result clearly.

Because beba is the direct object of the verb probudi, so it must be in the accusative case.

• nominative: beba = baby
• accusative: bebu = baby

Compare:

• Beba spava. = The baby is sleeping.
  Here beba is the subject.
• Zvono probudi bebu. = The bell wakes the baby.
  Here bebu is the object.

For many feminine nouns ending in -a, the accusative singular ends in -u.

Croatian normally has no articles like English a/an/the.

So:

• zvono can mean a bell or the bell
• bebu can mean a baby or the baby, depending on context

The sentence could therefore be understood as:

• The bell is so loud that it wakes the baby
• or A bell is so loud that it wakes a baby

Usually context tells you which one is meant.

Here it is an adjective.

That can be confusing, because glasno can also look like an adverb meaning loudly. But in this sentence it is part of the predicate with je and describes zvono.

• Zvono je glasno. = The bell is loud.
  Here glasno is an adjective.
• On govori glasno. = He speaks loudly.
  Here glasno is an adverb.

The form looks the same, but the function is different.

Je is the 3rd person singular present form of biti = to be.

Since zvono is singular, Croatian uses je:

• zvono je glasno = the bell is loud

Compare:

• Ja sam umoran. = I am tired.
• Ti si umoran. = You are tired.
• On je umoran. = He is tired.
• Zvono je glasno. = The bell is loud.

Yes, in many situations tako ... da ... and toliko ... da ... can both work and both can mean so ... that ...

• Zvono je tako glasno da probudi bebu.
• Zvono je toliko glasno da probudi bebu.

In practice, both are natural.
A rough distinction is:

• tako = so, in that way / to such a degree
• toliko = so much, to that extent

But in sentences like this, the difference is usually small.

Because here the verb is being used transitively: someone/something wakes someone else.

• probuditi bebu = to wake the baby
• beba se probudi = the baby wakes up

So:

• Zvono probudi bebu. = The bell wakes the baby.
• Beba se probudi. = The baby wakes up.

The reflexive se is used when the subject is the one that wakes up.

Not completely. Croatian word order is more flexible than English, though some versions sound more natural than others.

The given sentence is natural:

• Zvono je toliko glasno da probudi bebu.

You may also see variations for emphasis, such as:

• Toliko je glasno zvono da probudi bebu.
• Zvono je glasno toliko da probudi bebu.

But these can sound more marked or literary, and the original version is the safest one for learners.

It can suggest either, depending on context, but most naturally it expresses a result: the bell is loud enough to wake the baby.

Because probudi is perfective, it often gives the sense of a completed result, something like:

• The bell is so loud that it will wake the baby
• The bell is so loud that it wakes the baby up

If you wanted a more habitual or repeated sense, Croatian might choose a different wording, often with an imperfective verb or extra context.