[chemical substances]
   compounds
     Class isoprenoids
       Class terpenoids
         1 Class [hemiterpenoids] [C5 skeleton]
         2 Class monoterpenoids [C10 skeleton]
         3 Class sesquiterpenoids [C15 skeleton]
         4 Class diterpenoids [C20 skeleton]
         5 Class sesterterpenoids [C25 skeleton]
         6 Class triterpenoids [C30 skeleton] - terpenoids having a C30 skeleton
         7 Class tetraterpenoids [C40 skeleton] - terpenoids having a C40 skeleton
         8 Class [polyterpenoids] [C5n skeleton]