Mfuko wangu ni mchafu.

In Swahili, possessives agree with the noun class of the thing being possessed.

Mfuko belongs to the m-/mi- noun class in the singular, so -angu takes the matching agreement form wangu.

So:

• mfuko wangu = my bag / my pocket
• mifuko yangu = my bags / my pockets

The w- in wangu is there because it matches mfuko.

For the same reason: adjectives in Swahili also agree with the noun class.

The adjective root is -chafu = dirty.
When it describes mfuko, it takes the class prefix m-, becoming mchafu.

So:

• mfuko mchafu = dirty bag
• mifuko michafu = dirty bags

This agreement is very important in Swahili grammar.

Ni is the equivalent of is / am / are in this sentence. It links the subject to its description.

So:

• Mfuko wangu ni mchafu = My bag is dirty

Here:

• Mfuko wangu = the subject, my bag
• ni = is
• mchafu = dirty

Yes. Mfuko can mean:

• bag
• sack
• pocket

The exact meaning depends on context.

For example:

• Mfuko wangu ni mchafu could mean My bag is dirty
• In another context, it could also mean My pocket is dirty

If you want to be more specific, context usually makes it clear.

A simple pronunciation guide is:

m-FU-ko WAH-ngu nee m-cha-FU

A few helpful notes:

• mf at the start of mfuko is pronounced together, almost like saying the m and f back-to-back.
• ng in wangu is like the ng in finger, not like the ng in sing.
• ch is like ch in church.
• Swahili vowels are usually pure and consistent:
  • a = like a in father
  • e = like e in bet (or a bit tenser)
  • i = like ee in see
  • o = like o in go without much glide
  • u = like oo in food

Stress is usually on the second-to-last syllable:

• mfuKO
• WAngu
• CHAfu

The plural is:

Mifuko yangu ni michafu.

Breakdown:

• mfuko → mifuko = bag → bags
• wangu → yangu = my for the plural noun class
• mchafu → michafu = dirty in agreement with the plural noun

So:

• Mfuko wangu ni mchafu. = My bag is dirty.
• Mifuko yangu ni michafu. = My bags are dirty.

In Swahili, possessives usually come after the noun they describe.

So you say:

• mfuko wangu = bag my literally, but naturally my bag
• kitabu changu = my book
• rafiki yangu = my friend

This is normal Swahili word order.

Normally, for a full sentence meaning My bag is dirty, you should use ni:

Mfuko wangu ni mchafu.

Without ni, mfuko wangu mchafu sounds more like a noun phrase:

• my dirty bag

So the difference is:

• Mfuko wangu ni mchafu. = My bag is dirty.
• Mfuko wangu mchafu = my dirty bag

You keep mfuko and mchafu, but change the possessive:

• Mfuko wako ni mchafu. = Your bag is dirty.
• Mfuko wake ni mchafu. = His/Her bag is dirty.
• Mfuko wetu ni mchafu. = Our bag is dirty.
• Mfuko wenu ni mchafu. = Your (plural) bag is dirty.
• Mfuko wao ni mchafu. = Their bag is dirty.

Notice that the possessive forms still match the noun class of mfuko.

It can mean both literal and figurative dirty.

Literal:

• shati mchafu = a dirty shirt
• mfuko wangu ni mchafu = my bag is dirty

It can also describe something unclean, filthy, or even sometimes obscene / indecent, depending on context.

So it is a useful adjective, but context matters.

The pattern is:

[noun + possessive] + ni + [adjective]

In this sentence:

• mfuko = noun
• wangu = possessive
• ni = linking verb (is)
• mchafu = adjective

So the full structure is:

Mfuko wangu + ni + mchafu
My bag + is + dirty

This is a very common Swahili sentence pattern.