い-Adjective Conjugation: かったです vs でした


When we first studied adjective conjugation in my Japanese class, I kept
making the same mistake habitually; I would conjugate the past tense of
い-adjectives with でした at the end instead of dropping the い and adding かったです.
My teacher would correct me, and now I've more or less started doing かったです,
but I still wonder about how "wrong" adjective-でした is.

> ○ あのテストは難しかったです。
>
> ×? あのテストは難しいでした。

Is the second sentence straight out wrong and/or extremely unnatural-sounding?
Would anybody in Japan conjugate adjectives like this? Or does it possibly
introduce a _slightly_ different meaning?




`あのテストは難しいでした` to me sounds strange. If you search Google for `テストは難しいでした`,
you get about 10 results, many of them written by foreign speakers.
`テストは難しかったです` however gets far more results.

I wouldn't right out say that it's wrong to use `難しいでした` as you can find many
instances of it when you search for it. However, I think it's overwhelmingly
used by females when you look through the results. It's just a speculation of
mine, but it may sound slightly "cuter" or "younger" to use `難しいでした` as in
`確かに難しいでしたけれどーー字の雰囲気で何となく解りましたから――ー大丈夫でした` and similar examples.

That said, I think people learning Japanese should use `難しかったです` rather than
`難しいでした`.

**Disclaimer:** I'm not a native speaker, just my thoughts.




It is ungrammatical. No one will conjugate like that.

