Why do we say Kuro obi and not Kuroi obi

Good day,
While learning color adjectives, I came to ask myself the following question.
In martial art a black belt is said kuro obi and not korui obi.
Can some one help me understand ?
Thanks a lot

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When multiple words become one word mashed together, they often ignore any standard grammar connection rules.

Black cat in Japanese is くろねこ, not くろいねこ. Of course you could say くろいねこ, and it wouldn’t be “wrong,” but it’s become one word without the grammar to glue it together.

Similarly, we say 日本料理にほんりょうり, and not 日本にほん料理りょうり, even though the standard way of connecting nouns is with の.

Once you say something enough times together, it stops being thought of as two separate words that need connecting. Not that it necessarily happens literally like that… but it’s not that different in English. It’s just that with something like “black belt” or “black cat” we don’t have any grammatical difference for “black” the adjective and “black” the noun.


So black is an i-adjective 黒い (くろ・い), but the word for black belt is a compound 黒帯 (くろ・おび).

I’m not sure if this comes from the Japanese people dropping the i in speech or if i-adjectives were introduced later.

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Thanks a lot . This is very clear and now hat I read it , makes a lot of sense.


Thanks a lot. Word compound I realise that this is also part of japanese (sorry I am such a beginner)

I’d go further and say they outright contradict expectations to audibly reinforce that the words are inseparably compounded together as a single unit of meaning. Compounding also triggers rendaku too, like in あかがね (あか + かね “red gold” = copper).

English does its own compound marking, but since invading French aristocrats jettisoned all of English’s inflectional endings we use intonation and spelling conventions to mark compounds instead.

The stress and timing of “white board” and “whiteboard” differ plenty between “It’s not a yellow board, it’s a white board” (a board which happens to be white) and “Write the answer on the whiteboard” (the writing surface). Personally I’d say the latter quicker and with less emphasis on “board”, and the former is slower with about equal stress on both words. It’s still marking that something’s a bit different from the norm with how those two words relate to one another, but using different language features. :slight_smile:

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Thanks for extending the explanation.

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