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


As a disclaimer, I have read this link, [Why does Japanese have two kinds of
adjectives? (-i adjectives and -na
adjectives)](https://japanese.stackexchange.com/questions/1008/why-does-
japanese-have-two-kinds-of-adjectives-i-adjectives-and-na-adjective) 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




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

* * *

See also [Why can't だ be used after an
I-adjective?](https://japanese.stackexchange.com/questions/43244/why-
cant-%e3%81%a0-be-used-after-an-i-adjective/43246#43246)

* * *

Please comment if the above does not address your questions.

