Understanding the connection between adverbs and adjective negation

Question

い-adjectives negate in the following way.

「大{おお}きい」→「大きくない」

How I've always interpreted process is that we're basically changing the adjective 「大きい」 into the adverb form 「大きく」 and then tacking on 「ない」, which is itself an adjective describing negation.

One thing that seems weird is of course that「ない」is an adjective and not a verb, so why would our adjective need to be changed into an adverb first? Perhaps it is because in context we would see 「ないです」, which itself functions as a verb? So perhaps in the sentence 「大きくないです」, we are seeing an outer structure outer structure of 「大きく」 and an inner structure of 「ないです」.

Usually, I see 「大きくないです」 romanized as ookikunai desu instead of ookiku naidesu, so this makes me doubt my thinking.

Is the way I described above a correct way of interpreting this inflection? If not, what would be a proper way?

Answer 1

An adverb is used to modify not only a verb but also an adjective, both in Japanese and in English.

• とても良い = very good
  (とても and very are adverbs which (almost) exclusively modify an adjective)
• 酷くまずい = terribly yucky
  (酷く and terribly are "adverbial forms of adjectives" that modify another adjective. 酷くてまずい means "terrible, and yucky".)

So I think the ku-form is a natural choice to combine two adjectives. In Japanese grammatical terms, the ku-form is called 連用形, literally "connect-to-用言 form", where 用言 roughly means "verbs and adjectives".