Poslije kiše voda u jezeru je mutna.

Because poslije normally takes the genitive case.

• Base form: kiša = rain
• Genitive singular: kiše

So poslije kiše means after the rain.

You will see the same pattern with many nouns after poslije:

• poslije škole = after school
• poslije ručka = after lunch

Yes. Poslije and nakon both mean after and both are commonly used with the genitive.

So these are both natural:

• Poslije kiše voda u jezeru je mutna.
• Nakon kiše voda u jezeru je mutna.

There can be slight stylistic differences depending on region or speaker, but for a learner, both are correct and useful.

Because u can be followed by different cases depending on the meaning.

Here it means in the lake, describing a location, so Croatian uses the locative case:

• jezero = lake
• u jezeru = in the lake

If there were movement into the lake, Croatian would usually use the accusative:

• u jezero = into the lake

So:

• voda u jezeru = the water in the lake
• baciti nešto u jezero = to throw something into the lake

Because it agrees with voda, and voda is a feminine noun.

In Croatian, adjectives must agree with the noun in:

• gender
• number
• case

Here:

• voda = feminine singular
• so the adjective is mutna = feminine singular

Compare:

• voda je mutna = the water is murky
• sok je mutan = the juice is murky (masculine)
• more je mutno = the sea is murky (neuter)

The two je forms are doing different jobs in the sentence.

1. In u jezeru, the letters je are just part of the word jezeru. That is not the verb.
2. The separate word je is the verb to be in the present tense, third person singular:
   • voda ... je mutna = water ... is murky

So there is only one actual verb je in the sentence.

The structure is:

Poslije kiše / voda u jezeru / je mutna

So:

• Poslije kiše = time expression
• voda u jezeru = subject noun phrase
• je mutna = predicate

A more grammar-based breakdown:

• voda = subject
• u jezeru = prepositional phrase describing which water
• je = verb
• mutna = predicate adjective

Yes. Croatian word order is more flexible than English word order.

The sentence:

• Poslije kiše voda u jezeru je mutna.

could also appear as:

• Voda u jezeru je mutna poslije kiše.
• Poslije kiše je voda u jezeru mutna. (less neutral, but possible in context)

The original version sounds natural and neutral because it starts with the time phrase after the rain and then gives the main statement.

Even though word order can change, the cases still show the grammatical relationships.

Usually in this kind of sentence, yes: mutna means murky, cloudy, or not clear, especially for water.

The adjective comes from mutan / mutna / mutno.

With liquids, it often means:

• not transparent
• dirty-looking
• cloudy from stirred-up material

So in this sentence, it describes the water becoming unclear after rain.

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

So:

• voda can mean water, the water, or sometimes some water, depending on context.
• u jezeru can mean in the lake or in a lake, again depending on context.

The exact meaning comes from the situation, not from an article.

It works together as one noun phrase: voda u jezeru = the water in the lake.

• voda is the main noun
• u jezeru specifies which water

So u jezeru is attached in meaning to voda, not to mutna.

That is why the sentence means:

• the water in the lake is murky not
• the water is murky in the lake as a separate adverbial idea

Here voda is in the nominative singular, because it is the subject of the sentence.

Its basic dictionary form is also voda.

So:

• voda = nominative singular
• it matches the verb je
• and the adjective mutna agrees with it

Yes, it is natural and clear.

It sounds like a normal descriptive statement, especially in a context about nature, weather, lakes, or water quality.

A native speaker might also say similar things like:

• Poslije kiše rijeka je mutna. = After the rain, the river is murky.
• Poslije kiše voda je mutna. = After the rain, the water is murky.

So the sentence is a good example of everyday Croatian grammar.