What does 'na' at the end of a word mean?


I saw many questions regarding "na" at the end of a sentence; however, what
about at the end of a word? Consider these two sentences:

>   1. Korewa ōki **na** kurumadesu. (これはおおき **な** くるまです) _This is a big car_.
>
>   2. Ōkii kurumadesu. (おおきいくるまです) _(This) is a big car._
>
>

What does 'na' (bolded) have to do in this sentence?

Consider this sentence too:

> Korewa akai kurumadesu. (これはあかいくるまです) _This is a red car_.

How come 'na' is used in the first sentence but not in this one. Does 'na'
mean 'a' as an article?




In the 連体形{れんたいけい} (attributive form) of a na-adjective, な comes at the end of
it, like 静{しず}かな, きれいな.

In the 連体形 (attributive form) of an i-adjective, い comes at the end of it,
like 大{おお}きい, 暑{あつ}い. That is the same as the dictionary form.

大きな is the 連体形 (attributive form) of an old na-adjective おおきなり, and only the
attributive form is used in the present day. 小{ちい}さな, おかしな are also the same
thing. They are analyzed as pre-noun adjectivals but are a bit different from
other pre-noun adjectivals.

So both 大きい車{くるま} and 大きな車 are used, and they have almost the same meaning.

