Think requires Learn. Contemplate requires Think. 
Pen is etymologically related to Feather. Feather is part of Bird. you are likely to find Bird in/at/on Forest. Forest is a type of Single. 
Learn <--HasPrerequisite-- Think <--HasPrerequisite-- Contemplate 
Pen --EtymologicallyRelatedTo--> Feather --PartOf--> Bird --AtLocation--> Forest --IsA--> Single 