全然 {ぜんぜん} with positive adjective / na-adjective

Question

In Japanese classes, I was taught that 全然 can only be used with negative-meaning words/phrases/clauses, for example:

全然出来ません
全然だめです

However, I've observed that, especially in spoken Japanese, some positive na-adjectives are allowed to follow 全然 adverb, for example:

全然平気です
全然大丈夫です

Or even:

全然OKです

Are there any reasons why these na-adjectives do not have to follow the 全然+negative rule? Given any other na-adjective with positive meaning, how to decide whether or not I can use it with the 全然 adverb? (e.g. 全然きれい)

p/s: I am fully aware that we have to look at the full sentence to determine whether the word/phrase/clause that follows 全然 is positive or negative, for example: {大丈夫じゃない} has negative meaning so {全然大丈夫じゃない} is OK. But I hear {全然大丈夫です} a lot in anime/drama, hence this question.

Answer 1

Like YOU mentioned, Zenzen being used with positive words is slang and not correct Japanese. That being said, Japanese people use it all the time, especially young people.

Typically I hear 全然 with OK、大丈夫、平気, 楽しい、and きれい with others possibly I haven't heard. That is to say that the words that are used with 全然 in a positive sense are probably limited to just a few words, but because language is living, this list will probably change.

Total off shoot, these words listed above seem like words a ギャール uses all the time and can't get that image out of my mind.

Answer 2

YOU and Mark have already mentioned that 全然 can be used with a small set of positive descriptions, and that this is usage is not considered correct (which might be true, but it's absurdly common, so that doesn't really matter).

But my impression is that the positive version of 全然 is not really limited to a small set of words, but rather to particular situations. The situations I've seen the positive 全然 are all situations where there's an expectation of something "not being X" but it actually "is X". For instance, you'd usually say 全然OKです when someone asks you if something is okay with you and you see that he's not sure whether it is - so you assure him that his negative expectations are completely unfounded and it's completely okay. The same thing happens with the example YOU gave about 全然きれい:

A：　私この服似合ってるかしら？
B：　全然きれいですよ。

A is not sure whether her new clothes look good on her, so she asks for B's opinion. B assures her that they do look beautiful.

On the other hand, this usage of 全然きれい is probably incorrect:

A：　その服すごく似合ってるね。 B：　そうね。全然きれいよ！

Because here B's saying wasn't against A's (or anyone's) expectations.

Answer 3

全然　has slang form, which means like exceptionally, extremely.

So you can use it in both forms.