怖い indeed means both "to be scary" and "to be scared" depending on the context. You may feel this is insane, but English has similar examples, too, so let me explain about this first.
In English, "I am sad" means this person is feeling sorrow, but "The news is sad" does not mean this news is feeling sorrow. Why? Because "sad" has two distinct meanings, "to ...
だ is the plain-form copula (the "is; to be" word). In the plain form, い adjectives already form a complete predicate (the piece of a sentence or clause that can complete that sentence or clause). In translation, it's like the い adjective already includes the "is" meaning -- so 速い would be "[it] is fast", not just "fast".
Since だ is only used to provide a ...
To give a few working examples:
I'm scared of cats.
Emiko seems to be fine around cats, but apparently is scared of me.
I'm scary, just so you know.
That makes 私は怖い officially ambiguous and the answer to your question must be "both, depending on the context".
Your "usual rule" is incomplete. It should be:
if resulting is a single mora in length, add -sa
na + sa
na + sa + sou --> nasasou.
atu + sou --> atusou.
Grammatically speaking, there really are no adjectives in Japanese. i-adjectives are just special verbs. i-adjectives have many of the same inflections as do verbs, and they fulfill a grammatical role essentially equivalent to that of verbs. Therefore, 電車は速い is a complete sentence meaning "the train is fast", where 速い is the predicate.
i-adjective + です ...
As answered, 少ない is not a negative form of an adjective, but rather already the dictionary form.
It is only coincidentally pronounced the same way as the negative form of other い-adjectives.
It might be interesting to know that the dictionary entry of すくない also shows alternative kanji (including archaic versions), where the only kana visible after the ...
Thanks to snailplane's and Dono's links, it seems that the answer is fairly established:
Namely, 〜ない is also a suffix that attaches onto words describing state or quality, turns them into a 形容詞, and emphasizes them.
Arguing about whether certain words "are" something or other is missing the point in this context, I think. We do not classify words based on some innate, a priori nature that we discern within them. We classify them based on behaviour. And there is no a priori set of standards for that classification either: we have to choose our own. It's completely ...
There are at least three types of omission of く, which should be distinguished.
The "traditional western" euphoric change is called ウ音便 and is described in this question, this one and a chart in this page. ku becomes (y)u, etc. This sounds old-fashioned and elegant. While this is commonly heard in samurai dramas, only a few courteous elder people use this ...
"Aがこわい" commonly means "A is horrible(scary)", "I am scared of A". So 私がこわい is commonly interpreted as "I am horrible(scary)". For example, 昨日、友達に意地悪をしてしまった。私がこわい.
If you want to say "I am scared", you can say "私はこわい", "私はこわがっている".
However, "Aはこわい" can mean both "A is horrible(scary)" and "A is scared", so if you clearly want to mean ""A is scared", you ...
It's uttered as a colloquial, casual and exclamatory phrase. It's typically used in response to a situation/stimulation that strikes you suddenly. っ is often added after the stem.
高っ! (Wow,) it's expensive!
やば(っ)! (Wow,) this is bad!
In formal settings, you should generally avoid this, but no one would blame you for ...
nasi and nai are the same word. Like all adjectives, nasi is the conclusive form (終止形), while nai is the attributive form (連体形). More specifically, the attributive ends in naki, but the medial -k- drops out in modern Japanese becoming nai. This is true of all adjectives: atusi -> atuki > atui, takasi -> takaki > takai, muzukasi -> muzukasiki > muzukasii etc. ...
Modern Japanese is very different from archaic Japanese (and some modern formal written Japanese, which is itself rather archaic) in regard to the topic at hand. Initially there were distinct conjugations of verbs and adjectives known as predicative and attributive. Predicative (also called conclusive) was used for the final verb in a sentence, and was ...
Is it by any chance the case that, historically, the い-adjective ending 〜かった is a contraction originating from 〜くあった, where あった is the past inflection of ある?
That's exactly what you're seeing.
For ～い adjectives, there were three base conjugation forms:
～し -- 終止形【しゅうしけい】: terminal / conclusive, for ending a sentence of clause.
～き -- 連体形【れんたいけい】: ...
there is perhaps some historical connection between the く sound and い sound, either phonologically or semantically.
I think the answer from blutorange addresses this.
Maybe these two classes of words [〜い adjectives and 〜く verbs] diverged from the same class of words somehow?
I'll disagree with blutorange about this part, as his answer is (I believe) ...
The standard form is おもしろくて仕方ない, where おもしろくて is used as an adjective (not adverb) in the て-form for connecting predicates.
(て-form adjective) + 仕方ない
(たい-form verb in て-form) + 仕方ない
is a common phrase that means “It's so (adjective)” or “I really want to (verb)”. The nuance of this 仕方ない is “I can't stand it”, but it's not to be taken literally, ...
好きくない is indeed not proper grammar. It is sometimes used by children (and hence in fiction for children or childlike characters), reanalyzing 好き which should be a na-adjective 好き（な） as an i-adjective *好きい, hence *好きくない or *好きかった.
有名 is a na-adjective and thus is followed by だ・で・な・に (or by じゃ < では)
lit. that person is famous
lit. that person is a famous person
lit. that person is surely going to become famous
You can think of ではありません or じゃありません as the negative of です (which in turn is the polite form of だ whose negative would be ...
In this specific case, yes, 青空 and 青い空 both mean "blue sky". When used on their own, there is no surprising connotation and thus they are interchangeable. But 青空～ in a compound noun can mean "open-air" or "outdoor" (e.g., 青空教室 is not the same as 青い空教室).
Note that it's not always true for similar pairs. 白紙 is not the same as 白い紙, and 赤本 is not the same as ...
This is not a 'productive' grammar. There are certain cases (e.g. 近い・近くの、多い・多くの) where there are both noun and i-adjective forms, but you don't generally see "高くの". Where the noun form exists it will generally have a dictionary entry as well. And of course, there are only a few basic colours which even have the i-adjective form.
For the colours, I'm ...
This is an interesting topic but I think the question could stand to be a bit more focused. I will throw out an answer in an attempt to inspire other people to dig up better info and perhaps the OP to make the question more specific and answerable.
So "what is happening", in general terms to avoid specific theoretical assumptions:
In certain kinds of ...
As others have argued, it's pretty much a question of definition. But it seems obvious that in form, there's overlap between i-adjectives and plain verb-negatives.
I'm going to try to be constructive about it by starting a list of forms that exist in either or both of the cases. Please add or comment (or fix my formatting) as you see fit.