Natura - nature actualia - actual entities Mundus Plinius - physical world naturalia - natural bodies "crystal-kingdom" chemical substances chemical compounds Class amides [RkE(=O)l(OH)m (l≠0; ≥1 (OH):=(NR2))] Class primary amides [acyl-NR2] Class sulfinamides [RS(=O)NR2] - amides of sulfinic acids