What's the deal with "na" adjectives and "i" adjectives?

[Houndstooth]

Hey y’all, I’ve got a question regarding Japanese adjectives that I haven’t had any luck finding on Google or the forums.

I understand how they function and conjugate, but my question is why are they split into 形容動詞 and 形容詞? Obviously I mean besides by the way they end. Like are they different types of adjectives? Do they originate from different places? I’m curious as to why in English we just have “adjectives”, but Japanese, for some reason, has two kinds.

Thanks in advance for any and all help and information!

[Leebo]

な adjectives are basically nouns that need な to modify another noun. I don’t know the history though.

Another thing is, I believe い adjectives are a closed category, meaning new ones no longer get coined.

I’d be interested in learning more, but I wouldn’t take the fact that we call them both some kind of adjective in English to mean anything.

[Voi]

I found this interesting stack exchange:

https://japanese.stackexchange.com/questions/1008/why-does-japanese-have-two-kinds-of-adjectives-i-adjectives-and-na-adjective

I particularly liked the comparison to English up near the beginning, with how we essentially have nouns used like adjectives as well–their example was “winter clothes”.

[Houndstooth]

This is exactly the kind of super insightful explanation I was looking for, thanks! Definitely an interesting read.

@Leebo Realistically, this is exactly what you said, just with way more words

[Darcinon]

Often (but not always), the kanji in ~な adjectives use on’yomi readings, and the kanji in ~い adjectives use kun’yomi readings. I don’t know anything about why though.