Drift is a synonym of Float. Float is a different concept from Sink. 
Hill is related to Grade. Grade is a synonym of Mark. Mark is a synonym of Check. Check is a type of Weave. 
Drift <--Synonym--> Float <--DistinctFrom--> Sink 
Hill <--RelatedTo--> Grade <--Synonym--> Mark <--Synonym--> Check --IsA--> Weave 