Kitabu changu ni tofauti na kitabu cha Juma.

Because kitabu belongs to the ki-/vi- noun class, and possessives must agree with the noun class.

• kitabu = book
• changu = my, agreeing with a ki- class noun

So:

• kitabu changu = my book

If you used yangu, that would be the possessive form used with a different noun class, so it would not match kitabu.

In Swahili, possession is often expressed with -a plus a form that agrees with the noun being possessed.

Since kitabu is in the ki-/vi- class, the possessive linker becomes cha:

• kitabu cha Juma = Juma's book / the book of Juma

So cha here does not mean of all by itself in every situation; it is the agreement form of the possessive connector for this noun class.

Compare:

• kitabu cha Juma = Juma's book
• vitabu vya Juma = Juma's books

The connector changes with the noun class.

Ni is the copula, the word used for is / are / am in many Swahili sentences.

So:

• Kitabu changu ni tofauti na kitabu cha Juma.
  = My book is different from Juma's book.

Without ni, the sentence would be incomplete in standard Swahili for this kind of structure.

tofauti na means different from.

In this sentence:

• tofauti = different / difference
• na = from, in this expression

So the whole phrase:

• ni tofauti na = is different from

This is important because na often means and or with, but after tofauti, it is understood as from.

That is a very common question. Na has several uses in Swahili, and its meaning depends on context.

Common meanings include:

• and
• with
• as part of fixed expressions like tofauti na = different from

So in this sentence, you should learn tofauti na as a unit:

• tofauti na = different from

It is not being used here in the simple sense of and.

Yes, you often can leave it out if the meaning is already clear.

The full sentence is:

• Kitabu changu ni tofauti na kitabu cha Juma.

A shorter version is:

• Kitabu changu ni tofauti na cha Juma.

This still means:

• My book is different from Juma's.

The longer version is more explicit. The shorter version is very natural when it is obvious that cha Juma refers to kitabu cha Juma.

It behaves a little differently from many adjectives English speakers expect.

In sentences like this, tofauti is commonly used in the expression:

• kuwa tofauti na = to be different from

So while you can think of it as carrying the meaning different, it is often safest for learners to memorize the pattern:

• X ni tofauti na Y = X is different from Y

That will help you use it naturally without worrying too much at first about whether it should be labeled strictly as an adjective or noun.

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

So:

• kitabu can mean a book or the book
• the exact meaning depends on context

In this sentence, English translation may use my book and Juma's book, but Swahili does not need separate article words.

The noun itself shows that.

• kitabu = singular, book
• vitabu = plural, books

This noun belongs to the ki-/vi- class:

• singular prefix: ki-
• plural prefix: vi-

So if the sentence were plural, it would change like this:

• Vitabu vyangu ni tofauti na vitabu vya Juma.
  = My books are different from Juma's books.

Notice that the possessives also change:

• changu → vyangu
• cha Juma → vya Juma

A simple pronunciation guide is:

• Kitabu = kee-TAH-boo
• changu = CHAH-ngoo
• ni = nee
• tofauti = toh-fah-OO-tee
• na = nah
• kitabu = kee-TAH-boo
• cha = chah
• Juma = JOO-mah

A rough full pronunciation:

• kee-TAH-boo CHAH-ngoo nee toh-fah-OO-tee nah kee-TAH-boo chah JOO-mah

Swahili pronunciation is generally regular, so once you learn the sound system, words are usually pronounced the way they are written.