Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
monotonous [məˈnɔtənəs] adj (life, job etc) однообра́зный*однообра́зен (voice, sound) моното́нный*моното́нен
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: