Mnyama huyo ni nadra.

In Swahili, demonstratives such as this and that usually come after the noun, not before it.

So:

• mnyama huyo = that animal
• not usually huyo mnyama as the neutral basic order

This is a very common difference from English word order.

Huyo is a demonstrative for a singular animate noun in this noun class, and it usually means that.

Very roughly, you can compare:

• huyu = this
• huyo = that (often near the listener, or already mentioned)
• yule = that over there

So mnyama huyo is specifically that animal, not this animal.

Mnyama is singular, and its plural is wanyama. That puts it in the m-/wa- pattern, often called class 1/2.

Because of that, words that agree with it use the class 1 singular form, including the demonstrative huyo.

Compare:

• singular: mnyama huyo
• plural: wanyama hao

So huyo matches mnyama grammatically.

Ni is the copula here, the word that works like is/are in English.

So in Mnyama huyo ni nadra, ni links the subject and the description:

• Mnyama huyo = the animal being talked about
• ni = is
• nadra = rare

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

• Mnyama huyo ni nadra = That animal is rare.
• Wanyama hao ni nadra = Those animals are rare.

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

Instead, definiteness is usually understood from:

• context
• word order
• demonstratives like huyu, huyo, yule

So mnyama huyo is naturally understood as that animal, and there is no separate word for the.

Because nadra is commonly used as an invariable descriptive word here. In other words, it stays nadra instead of changing its form.

Some Swahili adjectives show noun-class agreement very clearly, but others do not. Nadra is one of the words that is often used without changing form, especially after ni.

So:

• Mnyama huyo ni nadra
• Wanyama hao ni nadra

In both cases, nadra stays the same.

Yes, functionally it works like rare in English. It is describing the animal.

In this sentence, it is being used as a predicate adjective-like word after ni:

• ni nadra = is rare

So even if Swahili grammar does not always behave exactly like English adjective grammar, the easiest way to understand it here is that nadra is describing the noun.

You would change the noun and the demonstrative:

• Mnyama huyo ni nadra = singular
• Wanyama hao ni nadra = plural

Here:

• mnyama → wanyama
• huyo → hao

Notice that ni and nadra stay the same.

You would usually replace ni with si:

• Mnyama huyo si nadra.

That means That animal is not rare.

So for this type of sentence:

• ni = is/are
• si = is not/are not

For a learner, the safest and most natural pattern is noun + demonstrative:

• mnyama huyo

That is the standard neutral order you should learn first.

You may sometimes see other orders in special contexts, but mnyama huyo is the normal form to use.