Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class ethers [ROR (R≠H)]
                 Class epoxy compounds (─O─ bridge)
                   Class epoxides [~R2COCR2~]
                     1 oxirane [C2H4O; ~O[CH2]2~]
                     2 2-ethyl-2-methyloxirane [C5H10O; ~OC(CH3)(CH2CH3)CH2~]