Katakana Adjectives

Adjectives that use borrowed words (usually from English) are notable because they are ALWAYS written in Katakana. These are NEVER "い" adjectives. They use ”な” such as the some Japanese adjectives like きれい do.
(kirei na = pretty/neat/tidy)

Some examples are :
COOL　クール（な）
and
SMART　スマト　（な）「As in stylish]

Being as such, they follow all the 'na' rules that Japanese has.

:)