Forbid is a type of Command. Command is a synonym of Require. Require is related to Payment. Payment is related to Salary. 
Drop is related to Liquid. Liquid is related to Mud. Mud is related to Earth. 
Forbid --IsA--> Command <--Synonym--> Require <--RelatedTo--> Payment <--RelatedTo--> Salary 
Drop <--RelatedTo--> Liquid <--RelatedTo--> Mud <--RelatedTo--> Earth 