Mwamba ni mkubwa.

Ni is the linking word in the sentence. Here it works like English is.

So the pattern is:

Mwamba + ni + mkubwa
rock + is + big

A useful thing to remember is that ni does not change for singular and plural in this kind of sentence.

• Mwamba ni mkubwa = the rock is big
• Miamba ni mikubwa = the rocks are big

Because adjectives in Swahili usually have to agree with the noun class of the noun they describe.

The adjective stem is -kubwa, meaning big / large.
Since mwamba belongs to a noun class that takes an m- agreement prefix in the singular, the adjective becomes:

m- + -kubwa → mkubwa

So:

• mwamba mkubwa = big rock
• Mwamba ni mkubwa = the rock is big

Mwamba is a singular noun in the m-/mi- class pair, often called Class 3/4.

That matters because many other words must match its class, especially:

• adjectives
• demonstratives
• some verb agreements
• possessives

For this sentence, the important effect is on the adjective:

• singular: mwamba mkubwa
• plural: miamba mikubwa

So the class of mwamba is the reason you see m- in mkubwa.

The plural is:

Miamba ni mikubwa.

Changes:

• mwamba → miamba
• mkubwa → mikubwa

Both the noun and the adjective change to match the plural noun class.

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

So Mwamba ni mkubwa can mean things like:

• The rock is big
• A rock is big
• That rock is big

The exact meaning depends on context, not on a separate article word.

No.

Mwamba mkubwa is usually a noun phrase, not a full sentence. It means:

big rock

But Mwamba ni mkubwa is a full sentence:

The rock is big

So the presence of ni is important here.

• mwamba mkubwa = big rock
• Mwamba ni mkubwa = the rock is big

Not always.

-kubwa often means big or large, but depending on context it can also mean things like:

• important
• great
• older / elder
• senior

With an object like mwamba, the most natural meaning is physical size: big.

But with a person, for example, mkubwa might mean important or older, depending on context.

A simple English-friendly guide:

• mwamba ≈ MWAM-ba
• mkubwa ≈ m-KOO-bwa

A few tips:

• mw is pronounced together, like a quick m followed by w
• u in Swahili is usually like oo in food
• stress is usually on the second-to-last syllable

So:

• mwam-ba → stress on mwam
• mku-bwa → stress on ku

For this sentence, the safest answer is: keep it.

If you remove ni, you get:

Mwamba mkubwa

That is normally understood as big rock, not the rock is big.

So for a learner, it is best to treat ni as necessary in this kind of basic statement.

Here it is capitalized simply because it is the first word of the sentence.

The common noun itself is normally written mwamba in the middle of a sentence.

So:

• Mwamba ni mkubwa. = capitalized because it starts the sentence
• Ninaona mwamba mkubwa. = lower-case in the middle of a sentence

It does not automatically mean it is a proper name.