Kad je u kući tišina, lakše zaspim.

It literally works like in the house is silence. Natural English would usually say there is silence in the house or it is quiet in the house.

Grammatically:

• u kući = in the house
• je = is
• tišina = silence

So Croatian is using a noun, tišina, to express the state of quietness.

Because u can take different cases depending on meaning:

• u + locative = location, in
• u + accusative = direction, into

Here there is no movement; it describes where the silence is. So Croatian uses the locative:

• u kući = in the house
• u kuću = into the house

Also, kući is the locative singular form of kuća.

Croatian can express this idea in more than one natural way.

• Kad je u kući tišina... = When there is silence in the house...
• Kad je u kući tiho... = When it is quiet in the house...

Both are correct. Using tišina focuses on silence as a thing or state. Using tiho describes the environment as quiet. The meaning is very similar, but tišina sounds slightly more noun-based and concrete.

Lakše is the comparative adverb of lako.

• lako = easily
• lakše = more easily

So lakše zaspim means I fall asleep more easily.

Croatian often uses the comparative even when the second half of the comparison is not stated explicitly. The idea is understood from context.

Because these are different verbs:

• zaspati = to fall asleep
• spavati = to sleep

So:

• zaspim = I fall asleep
• spavam = I sleep / I am sleeping

The sentence is about the moment of falling asleep being easier, not about sleeping in general.

Yes. Zaspati is a perfective verb, but its present-tense form can still be used in sentences about repeated or general situations, especially in clauses like this.

So Kad je u kući tišina, lakše zaspim means something like:

• When the house is quiet, I fall asleep more easily
• Whenever there is silence in the house, I fall asleep more easily

This is a normal use of a perfective present in Croatian.

Usually it sounds like a general truth or habit: whenever the house is quiet, falling asleep is easier for the speaker.

So the sense is not usually right now, at this exact moment, but rather a repeated pattern.

Yes. Croatian word order is flexible. For example, these are all possible:

• Kad je u kući tišina, lakše zaspim.
• Lakše zaspim kad je u kući tišina.
• Kad je tišina u kući, lakše zaspim.

The basic meaning stays the same, but the emphasis changes slightly. The original version sounds very natural and smoothly sets the scene first, then gives the result.