Conventional is a synonym of Normal. Normal is related to Plain. Plain is related to Simple. 
Part is related to Day. Day is a different concept from Second. Second is related to Coat. Coat is related to Thick. 
Conventional <--Synonym--> Normal <--RelatedTo--> Plain <--RelatedTo--> Simple 
Part <--RelatedTo--> Day <--DistinctFrom--> Second <--RelatedTo--> Coat <--RelatedTo--> Thick 