Biology is a type of Life. Life is related to Fate. Fatal is derived from Fate. 
Singer is related to Occupation. Occupation is a synonym of Interest. Interest is similar to Principal. Principal is a synonym of Client. 
Biology --IsA--> Life <--RelatedTo--> Fate <--DerivedFrom-- Fatal 
Singer <--RelatedTo--> Occupation <--Synonym--> Interest <--SimilarTo--> Principal <--Synonym--> Client 