Jinai ni kosa.

Here ni is the copula, the linking word that means is/are in sentences like X is Y.

So:

• Jinai = crime
• ni = is
• kosa = offense/fault/wrongdoing

A useful thing to remember is that ni does not change for singular or plural. It stays ni.

Swahili usually does not use articles like English a, an, and the.

So jinai can mean:

• crime
• a crime
• the crime

The exact meaning depends on context. In Jinai ni kosa, it is most naturally understood as a general statement.

Yes. This is a very normal pattern in Swahili:

noun + ni + noun

It is a basic way to say that one thing is another thing.

Examples of the same pattern:

• Mwalimu ni mtu. = A teacher is a person.
• Hiki ni kitabu. = This is a book.

So Jinai ni kosa follows a standard structure.

Not always. Kosa has a broad meaning range, including:

• mistake
• fault
• error
• offense
• wrongdoing

In this sentence, it is not the everyday English idea of a small mistake like getting an answer wrong. It has the broader sense of fault/offense/wrongdoing.

Because the sentence is making a general classification: crime is an offense or a crime is an offense.

English often does this too:

• A whale is a mammal.
• Honesty is a virtue.

Swahili does the same kind of thing here. The singular form is natural in a definition-like statement.

A simple pronunciation guide is:

• jinai = ji-NA-i
• ni = nee
• kosa = KO-sa

So the whole sentence is roughly:

ji-NA-i nee KO-sa

Swahili vowels are usually pronounced clearly and separately:

• a as in father
• i as in machine
• o as in for but without an English glide

You replace ni with si:

Jinai si kosa. = Crime is not an offense.

In noun-based sentences like this one, si is the usual negative form of ni.

Kosa has the plural makosa.

Jinai is usually a noun whose singular and plural look the same, so jinai can often mean either crime or crimes, depending on context.

So:

• kosa → makosa
• jinai → often jinai in both singular and plural

This is normal for many Swahili nouns, though not for all of them.

It is a real and correct word, but it can sound somewhat formal or legal depending on context.

In everyday language, learners may also come across uhalifu, which is another common word related to crime/criminality.

So jinai is fine, but it may feel a bit more formal than some other ways of talking about crime.

No. Ni does not change to match the noun class.

That is different from many other parts of Swahili grammar, where agreement is very important. In this sentence, the linking word stays simply ni, no matter what noun comes before or after it.