In japanese teaching adjective two kinds one is Keiyou-doshi = Na Adjective and I adjective
Na adjective and Noun is near kind of group words Noun can stop itself like Are ha densha(that's train) like call TAIGEN DOME noun stop noun itself As I say Na Adjective is near kind of group noun therefore number of the Na adjective use like a noun shinpai, shizuka, kirei, kirai, suki, etc show emotions or out-look mostly stop itself or use terminate form da there for same case not use da to complete sentence.