Expert is a type of Person. Specialist is a type of Expert. Specialist is related to Specific. Specific is similar to Unique. 
Half is the opposite of Whole. Item is a type of Whole. Item is related to Object. Center is a type of Object. 
Person <--IsA-- Expert <--IsA-- Specialist <--RelatedTo--> Specific <--SimilarTo--> Unique 
Half <--Antonym--> Whole <--IsA-- Item <--RelatedTo--> Object <--IsA-- Center 