Why is ひつよう considered a な adjective?


Im struggling to understand why Hitsuyou (ひつよう) is considered a な adjective.

From what I understand after reading about い adjectives we simply drop the
last い to make it negative, for example: さむい becomes 住むくない because we dropped
the last い and added くない to make cold become "not cold".

This is pretty simple to understand as each word we want to make negative
usually has an い on the end.

However, using this same rule to use じゃない for な doesnt make sense to me with
ひつよう as there is no な in the word.

Ive been reading through [this online
dictionary](https://jlearn.net/Dictionary/Browse/1487660-hitsuyou-%E3%81%B2%E3%81%A4%E3%82%88%E3%81%86-%E5%BF%85%E8%A6%81)
but still haven't been able to grasp why.

Can you help me understand?




For the so-called " _-na_ adjectives", the _-na_ only appears when the
adjective is used attributively -- when it used to modify a noun. When these
adjectives are used predicatively -- at the end of a sentence -- there is no
_-na_.

Examples:

  * この車【くるま】は静【しず】かです。 -- This car is quiet.  
これは静【しず】か **な** 車【くるま】です。 -- This is a quiet car.

  * この本【ほん】は必要【ひつよう】です。 -- This book is required / necessary.  
これは必要【ひつよう】 **な** 本【ほん】です。 -- This is a required / necessary book.

Note that じゃない negation can be used after both _-na_ adjectives and nouns, and
can be used both attributively (to modify a noun) and predicatively (at the
end of a sentence).

  * この車【くるま】は静【しず】か **じゃない** です。 -- This car is **not** quiet.  
これは静【しず】かな車【くるま】 **じゃない** です。 -- This is **not** a quiet car. (It could be a
loud car, or a slightly rattly car, or not even a car at all.)  
これは静【しず】か **じゃない** 車です。 -- This is a **not-** ​quiet car. (A bit clunky in
both the English and Japanese, but the meaning is clear.)

There's some more information over at
[Wikipedia](https://en.wikipedia.org/wiki/Japanese_equivalents_of_adjectives#na-
adjective) that might be useful.

If you are still confused, please comment and I can expand this answer.




For the so-called " _-na_ adjectives", the _-na_ only appears when the
adjective is used attributively -- when it used to modify a noun. When these
adjectives are used predicatively -- at the end of a sentence -- there is no
_-na_.

Examples:

  * この車【くるま】は静【しず】かです。 -- This car is quiet.  
これは静【しず】か **な** 車【くるま】です。 -- This is a quiet car.

  * この本【ほん】は必要【ひつよう】です。 -- This book is required / necessary.  
これは必要【ひつよう】 **な** 本【ほん】です。 -- This is a required / necessary book.

Note that じゃない negation can be used after both _-na_ adjectives and nouns, and
can be used both attributively (to modify a noun) and predicatively (at the
end of a sentence).

  * この車【くるま】は静【しず】か **じゃない** です。 -- This car is **not** quiet.  
これは静【しず】かな車【くるま】 **じゃない** です。 -- This is **not** a quiet car. (It could be a
loud car, or a slightly rattly car, or not even a car at all.)  
これは静【しず】か **じゃない** 車です。 -- This is a **not-** ​quiet car. (A bit clunky in
both the English and Japanese, but the meaning is clear.)

There's some more information over at
[Wikipedia](https://en.wikipedia.org/wiki/Japanese_equivalents_of_adjectives#na-
adjective) that might be useful.

If you are still confused, please comment and I can expand this answer.

