Kimse kusurunu fark etmedi.

In Turkish, kimse often means anyone / anybody on its own, but when it appears with a negative verb, the whole sentence means no one / nobody.

So:

• Kimse geldi. is not normal for Nobody came
• Kimse gelmedi. = Nobody came

That is what is happening in:

• Kimse kusurunu fark etmedi.

This is a very common Turkish pattern.

Because Turkish normally uses negative concord here. In other words, words like kimse and hiçbir şey usually go together with a negative verb.

So Turkish says, literally in structure:

• kimse ... etmedi
• nobody ... did not notice

But the real meaning is simply:

• Nobody noticed ...

This is normal Turkish grammar, not a double negative in the English sense.

Kusurunu can be broken down like this:

• kusur = fault, flaw, defect
• -u / -un = possessive part
• -nu / -u = accusative part, with a linking n

So kusurunu means his/her/its fault/flaw or, depending on context, your fault/flaw as the direct object.

Two possible analyses are:

• kusur-u-nu = his/her/its flaw
  • accusative
• kusur-un-u = your flaw
  • accusative

In many sentences, context tells you which one is meant.

That n is a buffer consonant.

When a noun already has a possessive suffix and then takes another ending like the accusative, Turkish often inserts -n- between them.

For example:

• kusuru = his/her/its flaw
• kusurunu = his/her/its flaw + accusative

That inserted n helps connect the suffixes smoothly.

Because it is the definite direct object of the verb.

The verb phrase is fark etmek = to notice. What did nobody notice? kusurunu.

In Turkish, specific/definite direct objects usually take the accusative. Here, it is not just a flaw in general, but the person's flaw / his-her flaw / your flaw, so the accusative is natural.

Fark etmek is a very common Turkish compound verb meaning:

• to notice
• to realize
• sometimes to become aware of

It is built from:

• fark = difference, distinction, awareness
• etmek = to do / to make

Many Turkish verbs are formed this way: a noun plus etmek.

So in this sentence:

• fark etmedi = did not notice

You should learn fark etmek as a whole expression.

Etmedi breaks down as:

• et- = do / make
• -me- = negative
• -di = past tense

So:

• etmedi = did not do / did not make

Inside fark etmek, it becomes:

• fark etmedi = did not notice

There is no extra personal ending here because third person singular in the past tense can be zero-marked after -di.

This is a normal Turkish subject–object–verb order:

• Kimse = subject
• kusurunu = object
• fark etmedi = verb

So it follows the common Turkish pattern of putting the verb at the end.

Turkish word order is flexible, though. You could move things around for emphasis, but this version is the most straightforward and neutral.

Yes. You could say:

• Hiç kimse kusurunu fark etmedi.

This also means No one noticed his/her flaw.

Compared with kimse, hiç kimse can sound a bit more explicit or emphatic, but both are very natural with a negative verb.

Yes, it can be.

As a form, kusurunu can mean either:

• his/her/its flaw or
• your flaw

The sentence by itself does not force only one reading. Context decides.

If you wanted to make it clearer, Turkish could add a pronoun:

• onun kusurunu = his/her flaw
• senin kusurunu = your flaw

But Turkish often leaves those pronouns out if the meaning is already clear from context.

Because Turkish often does not need one.

If the context already makes it clear whose flaw is being talked about, the possessive suffix is enough:

• kusurunu = his/her flaw

Adding onun is possible:

• Kimse onun kusurunu fark etmedi.

This would sound more explicit, and sometimes more emphatic, but it is not required.

Not exactly.

• hata usually means mistake / error
• kusur often means fault / flaw / defect / shortcoming

There can be overlap, but kusur can sound more like a personal fault, imperfection, or defect, while hata is more often a mistake in what someone did.

So in this sentence, kusurunu is likely something like his/her flaw, fault, or shortcoming, not just a simple mistake.

A very literal breakdown would be something like:

• Kimse = nobody / anyone
• kusurunu = his/her/your flaw
• fark etmedi = did not notice

So the structure is roughly:

• Nobody his/her flaw noticed-not

That sounds strange in English, but it helps show the Turkish grammar:

• subject first
• object before the verb
• negative past tense on the verb at the end