Odds is etymologically related to Odd. Odd is a synonym of Unusual. Unusual is a different concept from Normal. Normal is a synonym of Healthy. 
Singer is the opposite of Dancer. Dancer is a type of Person. Rider is a type of Person. Rider can Trainer. 
Odds --EtymologicallyRelatedTo--> Odd <--Synonym--> Unusual <--DistinctFrom--> Normal <--Synonym--> Healthy 
Singer <--Antonym--> Dancer --IsA--> Person <--IsA-- Rider --CapableOf--> Trainer 