Kosa la bili limeonekana.

La is the of-linker that agrees with the noun class of kosa.
Kosa is a class 5 noun, so the linker is la.

So:

• kosa la bili = error of the bill / billing error

If it were plural, the linker would change:

• makosa ya bili = bill errors

So the choice of la is about noun class agreement, not about gender.

The li- is the subject marker on the verb, and it agrees with kosa.

In Swahili, verbs usually show agreement with the subject. Since kosa is a class 5 noun, the verb takes li-:

• kosa ... li-meonekana

If the subject were plural makosa, the verb would change too:

• makosa ... ya-meonekana

So li- is basically the verb’s way of saying it, specifically for a class 5 noun.

-me- is the perfect marker. It often corresponds to English has/have or to a completed action/state that is relevant now.

So:

• limeonekana = has appeared, has been seen, or has become apparent

With something like an error, the idea is often:

• it has been noticed
• it has become visible/apparent

It can suggest both, depending on context.

The verb -onekana is related to -ona (to see), but -onekana means things like:

• be seen
• be visible
• appear
• become apparent

So with kosa (error), limeonekana often means:

• the error has been noticed
• the error has become apparent

It is not always a dramatic appeared in the sense of suddenly popping up. Very often it means came to light or was noticed.

Here, kosa is a noun meaning error, mistake, or fault.

You can tell it is a noun because:

• it is followed by la bili
• it acts as the subject of the verb
• the verb agrees with it using li-

So in this sentence, kosa is not functioning as a verb.

Swahili normally does not use articles like English a/an and the.

So kosa la bili can mean:

• a bill error
• the bill error
• an error in the bill

The exact sense depends on context.

This is very normal in Swahili, so you should not expect a separate word for the.

You would change both the noun and the agreement:

• Kosa la bili limeonekana. = singular
• Makosa ya bili yameonekana. = plural

Notice all the changes:

• kosa → makosa
• la → ya
• li- → ya-

That is a good example of how noun class agreement affects several parts of the sentence.

Yes, and it has a slightly different feel.

• kosa la bili often means a bill-related error or billing error
• kosa kwenye bili means more literally an error on/in the bill

So both can work, but:

• la bili sounds a bit more like a relationship or type
• kwenye bili points more directly to the location of the error

In many everyday situations, Kosa kwenye bili limeonekana may sound especially clear if you mean there is a mistake on a specific bill.

A simple syllable breakdown is:

• ko-sa la bi-li li-me-o-ne-ka-na

A few useful pronunciation points:

• every vowel is pronounced clearly
• Swahili spelling is very regular
• stress is usually on the second-to-last syllable of each word

So roughly:

• KO-sa
• LA
• BI-li
• li-me-o-ne-KA-na

Also, bili here is pronounced bee-lee, not like English bill.

Yes, it is understandable and natural.

It sounds like something you might say when an error has been detected or has become apparent. Depending on context, some speakers might also choose a more specific verb, such as one meaning has been discovered or has been found, but limeonekana works well for the idea that the error is now noticeable or evident.

So the sentence is a good, normal example of:

• noun class agreement
• the of-linker
• the perfect tense/aspect
• a common derived verb meaning be seen / appear / become apparent