Postby Javizy » March 9th, 2008 11:50 pm
First off, there's no distinction across politeness levels. I'm guessing you saw two different lessons covering different grammar.
To link both kinds of adjectives, you use the て-form, both in affirmative and negative sentences.
For affirmative and negative i-adjectives: remove final い and add くて.
おいしい > おいしくて
おいしくない > おいしくなくて
For na-adjectives, you attach the て-form of the copula, で, which changes to ではない when negated (では can be contracted to じゃ). ではない conjugates in the same way described above, so it becomes ではなくて.
かんたん > かんたんで
かんたんではない > かんたんではなくて
As for し, it can be used similarly to the above use of the て-form, but is more empathetic and can imply that what is being said is merely part of a longer list. You can translate it as something like '...among other things', or 'not only ... but also'. It can also be used across politeness levels, depending what comes before it.
i-adjective/verb + し
na-adjective/noun + だ/だった + し
彼女は面白くてきれいでやさしい人です。
Kanojo wa omoshirokute kirei de yasashii hito desu.
She's an interesting, beautiful, kind person.
彼女は面白いし、きれいだし、やさしいです。
Kanojo wa omoshiroi shi, kirei da shi, yasashii desu.
She's not just interesting, but beautiful and kind as well.