Apparent inconsistency in turning い-adjectives into nouns: 赤い→赤 vs 近い→近く


Consider these adjectives:

  * 赤い

  * 近い

The い-declension works for sentence ending as well as directly modifying a
noun:

Now if I want to express the adjective as a noun, for example I'm talking
about "red(noun)" instead of "a red(adjective) thing":

  * Remove `い` from `赤い` to obtain the noun `赤`.

Note that `く` can be appended to form `赤く` which exists as an adverb.

赤になる and 赤くなる are both possible with similar meaning. This leads me to
conclude that 赤 is independent from the 赤い which 赤く can be derived from.

But if I try the same thing for 近い I find that I have to add く for it to mean
a noun.

  * Step 1. Remove `い` from `近い` to obtain the fragment(for lack of a better word) `近`. `近` does not seem to be able to stand alone (or can it?).

  * Step 2. Append `く` to `近` to obtain `近く`1

But 近く also exists as 近く2 \- the adverb that can be derived from 近い.

What is Step 2? It is different from the く-declension for adverbial usage. Why
doesn't 赤い get a 赤く noun that is derived from Step 2?




You are considering both of these words from the point of view of
i-adjectives, but think differently.

> 赤 noun  
>  → 赤い/赤く adjective derived from a noun by attaching "-i/-ku"
>
> 近い/近く adjective  
>  → 近く noun derived from an adjective by [zero-
> nominalization](https://japanese.stackexchange.com/questions/4489)




You are considering both of these words from the point of view of
i-adjectives, but think differently.

> 赤 noun  
>  → 赤い/赤く adjective derived from a noun by attaching "-i/-ku"
>
> 近い/近く adjective  
>  → 近く noun derived from an adjective by [zero-
> nominalization](https://japanese.stackexchange.com/questions/4489)

