Ongezeko la gharama ni kubwa.

A word-by-word breakdown is:

• ongezeko = increase
• la = a linker meaning of, agreeing with ongezeko
• gharama = cost, expense, or costs/expenses depending on context
• ni = is
• kubwa = big, large, or great

So the structure is literally something like increase of cost(s) is big.

Because la agrees with the noun ongezeko, not with gharama.

In Swahili, this of-linker changes based on the noun class of the first noun.
Here, the head noun is ongezeko, which belongs to noun class 5, so the linker is la.

So:

• ongezeko la gharama = increase of cost(s)

Even though gharama may refer to plural costs, the linker still matches ongezeko, not gharama.

Ongezeko is a class 5 noun. Its plural is maongezeko, which is class 6.

Examples:

• ongezeko kubwa = a big increase
• maongezeko makubwa = big increases

This class pairing, 5/6, is very common in Swahili.

Because with the adjective stem -kubwa, class 5 singular normally appears as just kubwa with no visible class prefix.

So:

• ongezeko kubwa = a big increase
• ongezeko la gharama ni kubwa = the increase in costs is big

But in the plural, the agreement becomes visible:

• maongezeko makubwa = big increases

So the lack of an obvious prefix in kubwa here is normal.

Ni is the copula, meaning is.

It connects the subject ongezeko la gharama with the description kubwa:

• Ongezeko la gharama = the increase in cost(s)
• ni kubwa = is big / is large

In standard Swahili, ni is the normal way to make this kind of present-tense sentence.

In standard written and taught Swahili, you should keep ni here.

So the correct standard form is:

• Ongezeko la gharama ni kubwa.

You may sometimes hear omission in casual speech in some contexts, but for learners, it is best to treat ni as required in this kind of sentence.

It can be understood either way depending on context.

Gharama often works like a mass or collective noun meaning:

• cost
• expense
• costs
• expenses

So ongezeko la gharama can mean:

• an increase in cost
• an increase in costs

English forces you to choose more clearly, but Swahili often leaves that more flexible.

This sentence talks about the increase as a thing.

That is why it uses the noun ongezeko rather than a verb form.

Compare:

• Ongezeko la gharama ni kubwa.
  = The increase in costs is large.

• Gharama zimeongezeka.
  = Costs have increased.

Both are natural, but the focus is different:

• ongezeko focuses on the increase itself
• zimeongezeka focuses on what the costs did

No. Kubwa can also mean:

• large
• great
• significant
• serious

In this sentence, it does not mean physically big.
It means something more like:

• large
• substantial
• significant

So Ongezeko la gharama ni kubwa is best understood as The increase in costs is large/significant.

Yes, but the structure is a little different.

• Ongezeko la gharama ni kubwa.
  = The increase in costs is big.

• Ongezeko kubwa la gharama
  = a big increase in costs / the big increase in costs

In the first sentence, kubwa is the predicate after ni.
In the second, kubwa is directly describing ongezeko inside the noun phrase.

Both are correct.

A simple pronunciation guide is:

• o-nge-ZE-ko
• la gha-RA-ma
• ni KU-bwa

Swahili stress is usually on the second-to-last syllable.

A few notes:

• ng in ongezeko is like the sound in finger, not just n + g said separately
• gh in gharama is often pronounced as a voiced guttural sound in careful speech, but many speakers pronounce it close to a normal g
• bw in kubwa is pronounced together, roughly boo-ah but more tightly joined

So a natural rhythm is:

o-nge-ZE-ko la gha-RA-ma ni KU-bwa