Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
nature [ˈneɪtʃər] n (also: Nature) приро́да; (character) нату́ра; (sort) хара́ктер
by nature (person) по нату́ре; (event, thing) по приро́де
documents of a confidential nature докуме́нты конфиденциа́льного хара́ктера
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.