Confusion on the pedagogy of adjective conjugation and interpretation of helper verbs and adjectives

Question

As a disclaimer, I have read this link, Why does Japanese have two kinds of adjectives? (-i adjectives and -na adjectives) and it could be because it hasn't processed in my brain yet, but I'm not sure I'm closer to some of my answers below. I've never posted here before, so if it is better practice to link me somewhere else if it's already answered my question, that would be great too.

Hi. Just decided to delve deep into the technicalities of Japanese grammar. For reference, I've been watching CureDolly's videos (she says her method is based on Jay Rubin's approach, and she often contrasts with "textbook" information). I'm not sure if the "books" are right, Jay Rubin is wrong, but I'm confused on if this is a black white thing. Is this how Japanese linguists think of Japanese? Or how English linguists think of Japanese? Is this debated? Examples below.

I'm currently in a university Japanese class and just learned about adjectives. Now, I know that there is a distinction between 'Na adjectives" and "I adjectives", and that is predicative forms of na adjectives need a state of being copula to form a complete idea. 花がきれい（だ）。Contrastively, i adjectives have a state of being function built into the "い".

First question, in my previous phrase, an example like 花が赤い forms a complete sentence, and politeness marking is unnecessary. Why and how does the い have a state of being in this scenario?

Continuing, in plain Japanese, I understand that for I adjectives, they "conjugate" like this:

赤い（あかい）to あかく（ない）、あか（かった）、and あかく（なかった）。

Second question, why あかい not use the く in the stem? Does this have something to do with the fact that the state of being is shown with a verb, and non-existence with an adjective? Maybe this has to do with the answer of my first question.

Furthermore, the versions we learn in class (of course being polite), are the same as above with です at the end. What is the distinction between these and the plain Japanese from the last example? Are these just more polite?

Next, when な adjectives are used as a predicate, the polite forms we learn in class can be demonstrated as such:

静か（です）、静か（じゃないです）、静か（でした）、静か（じゃなかったです）。

If I am correct, na adjectives used as a predicate follow the same rules and use the same ending forms as nouns, or at least my textbook says so. Here is an example sentence of two grammatical sentences according to the textbook.

静か（じゃなかったです）。and キムさんは四年生じゃなかったです。

Two questions here. What do these sentences look like in PLAIN japanese? Second, why can I not use ありませんでした in the second sentence?

Thank you very much for your help in my efforts to get better at this interesting language.

ありがとうございます

Answer 1

You've got too much in here for one post, which I'm guessing may account for your downvote.

Let me try to keep it simple.

First question, in my previous phrase, an example like 花が赤い forms a complete sentence, and politeness marking is unnecessary.

Politeness marking is necessary for both い and な adjectives.

• Plain / informal:
  • 赤【あか】い
  • 綺麗【きれい】だ
• Polite / formal:
  • 赤【あか】いです
  • 綺麗【きれい】です

The plain い adjective already contains the basic predication function, and thus does not need the だ -- the だ only serves to mark the end of a predicate when the sentence does not already end in a predicative word (like an い adjective or a verb).

However, です does two things -- it marks the predicate (if needed), and it includes information about the formality register. For polite / formal contexts, ending in just an い adjective is a full predicate, but the い adjective alone includes no information about formality register -- so you need the です to provide that.

Why and how does the い have a state of being in this scenario?

Some linguists describe い adjectives instead as "stative verbs" -- they describe state, and they can close a predicate the same way that a verb can. They inherently include a kind of simple "to be" sense. This is just a property of this class of word in Japanese, and there isn't really much "why" to talk about.

If you want to go really deep, I recommend Bjarke Frellesvig's A History of the Japanese Language. He discusses a possibility that the い ending on modern い adjectives may have grown out of an ancient copular ("to be" verb) suffixing element.

Second question, why あかい not use the く in the stem?

Um... it does. Not sure what you're asking here? All of the adverbial or connective forms of い adjectives are created by replacing the い with く.

It's possible you're asking about the past-tense form. For 赤【あか】い, that's 赤【あか】かった, which has no く. In truth, the past-tense forms for all い adjectives are contractions of earlier ～く + あった. This あった is the simple past tense of the verb ある. Even the past tense of the negative has this: 赤【あか】くなかった = 赤【あか】く + なく + あった.

You might still encounter un-contracted form ～くあった in some texts, or the polite version ～くありました.

If I am correct, na adjectives used as a predicate follow the same rules and use the same ending forms as nouns, or at least my textbook says so.

Yes, basically speaking, this is correct.

What do these sentences look like in PLAIN Japanese?

• Polite / formal register:
  • 静か（じゃなかったです）。
  • キムさんは四年生じゃなかったです。
• Plain / informal register:
  • 静か（じゃなかった）。
  • キムさんは四年生じゃなかった。

Note that the negative ending ない functions grammatically the same as any other い adjective. For present or future tense plain / informal, it just ends in ない, and the past ends in なかった. For present or future or past polite / formal, you need the です to indicate the register (as described above).

Second, why can I not use ありませんでした in the second sentence?

You can. In general, this is slightly more formal than なかったです, and that formality carries over to un-contracting the preceding particle -- so the じゃ becomes では.

• ～じゃなかったです
• ～ではありませんでした

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See also Why can't だ be used after an I-adjective?

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Please comment if the above does not address your questions.