I am complete beginner and I've got a question that I wish to ask you: When
negating an i-adjective (-くない), should we, as in the affirmative form, omit
the declarative "だ"? For example, is it "あのゲームは楽しくないだよ！" or "あのゲームは楽しくないよ！".

Thanks!
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2014-03-13T23:34:04.663
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2014-03-14T00:16:34.533
2014-03-13T23:48:25.770
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grammar
Using declarative だ with negative i-adjectives
You cannot attach a 「だ」 directly to an i-adjective, either in its affirmative
or negative form. (But believe me, many Japanese-learners make this mistake.)

> Incorrect: 「[楽]{たの}しいだ」、「楽しくないだ」、「[大]{おお}きいだ」、「大きくないだ」, etc.

Attaching a よ or ね is correct and very natural --- affirmative or negative.

> Correct: 「楽しいね」、「大きくないよ」、「かわいいね」、「おいしくないよ」, etc.

If you absolutely MUST use a だ for some reason, you can do so by inserting a
「の」 or informally, a 「ん」 between the i-adjective and the 「だ」 --- affirmative
or negative.

> Correct:
> 「楽しいのだ」、「[小]{ちい}さいんだ」、「[高]{たか}いんだ」、「[赤]{あか}いのだ」、「かわいくないのだ」、「大きくないんだ」, etc.
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2014-03-13T23:53:46.913
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2014-03-14T00:16:34.533
2014-03-14T00:16:34.533
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answer
When negating an i-adjective, you change い for くない. The ない part is an
auxiliary i-adjective, so you should omit だ, just as you do for i-adjectives.

> 新幹線は速い。  
>  A bullet train is fast.
>
> 壊れた新幹線は速くない。  
>  A broken bullet train is not fast.
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2014-03-13T23:54:08.433
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2014-03-13T23:54:08.433
2020-06-17T08:18:27.500
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