I've been learning about conjugating i- and na-adjectives recently and I've stumbled onto something odd. I've seen two distinct ways of conjugating negative i-adjectives; the two ways are to replace い with either:
- くない (for present negative) or くなかった (for past negative) then add です at the end, or
- くありません (for present negative) or くありませんでした (for past negative).
I'll use 楽しい as an example:
楽しくないです。 OR 楽しくありません。==> It is not fun.
楽しくなかったです。 OR 楽しくありませんでした。==> It was not fun.
Are these two algorithms for conjugating negative i-adjectives equivalent? Is one better than the other? What are any differences between them? Is one more formal than the other? Is there anything I should know about the relative usage of these two algorithms? Any input will be appreciated.