Tanzania ni nchi kubwa.

ni is the Swahili copula, the word used to link the subject to what is being said about it. In this sentence, it works like is in English:

• Tanzania ni nchi kubwa.
• Tanzania is a big country.

A useful thing to know is that ni does not change for person or number the way English am / is / are does. It stays ni.

For example:

• Mimi ni mwalimu = I am a teacher
• Wao ni wanafunzi = They are students

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

So:

• nchi can mean a country, the country, or just country, depending on context.
• nchi kubwa can mean a big country or the big country, depending on the situation.

In this sentence, English naturally translates it as a big country, but Swahili does not need a separate word for a.

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

So:

• nchi kubwa = literally country big
• natural English = big country

This is normal Swahili word order:

• mtoto mdogo = small child
• kitabu kizuri = good book

So nchi kubwa follows the standard pattern: noun + adjective.

Swahili adjectives often agree with the noun class of the noun they describe. nchi belongs to the N class (often called noun class 9/10), and with many adjectives in this class, the agreement prefix is not visible.

So:

• nchi kubwa = big country
• nchi kubwa also = big countries in the plural, depending on context

That means kubwa stays kubwa here.

Compare with another noun class where the adjective changes clearly:

• mtoto mkubwa = big child
• watoto wakubwa = big children

With nchi, the form kubwa is already the correct agreeing form.

Here, nchi is understood as singular because the subject Tanzania is one country.

But an important point is that nchi has the same form in both singular and plural:

• nchi = country
• nchi = countries

So the number is often understood from context.

Examples:

• Tanzania ni nchi kubwa = Tanzania is a big country
• Nchi hizi ni kubwa = These countries are big

nchi is often tricky for English speakers.

A simple approximation is:

• nchi ≈ n-chee

More specifically:

• the n is pronounced
• ch sounds like the ch in church
• i sounds like ee in see

So it is something like n-chee, said smoothly as one syllable or very close to one syllable.

Yes, you can, and it would mean Tanzania is big.

The difference is:

• Tanzania ni nchi kubwa = Tanzania is a big country
  • This explicitly says Tanzania belongs to the category country.
• Tanzania ni kubwa = Tanzania is big
  • This only describes Tanzania as big, without repeating that it is a country.

So the version with nchi is a little fuller and more explicit.

Tanzania is a proper name, so it stays Tanzania. Proper nouns in Swahili usually do not change form the way common nouns do.

In this sentence:

• Tanzania = the subject
• ni = links the subject to the description
• nchi kubwa = what is being said about Tanzania

So the structure is straightforward:

• Tanzania
  • ni
    • nchi kubwa

Yes. This sentence has a very common and natural pattern:

• Subject + ni + noun phrase

Here:

• Tanzania = subject
• ni = copula
• nchi kubwa = predicate noun phrase

So the sentence structure is completely standard:

• Tanzania ni nchi kubwa
• Amina ni daktari
• Hiki ni kitabu kizuri

It is a good model for making similar basic sentences in Swahili.