Start is a synonym of Departure. Departure is related to Leave. Leave is a different concept from Stay. Stay is the opposite of Travel. 
Asleep is related to Nest. Nest is related to Tree. Tree is related to Part. Part is related to Bed. 
Start <--Synonym--> Departure <--RelatedTo--> Leave <--DistinctFrom--> Stay <--Antonym--> Travel 
Asleep <--RelatedTo--> Nest <--RelatedTo--> Tree <--RelatedTo--> Part <--RelatedTo--> Bed 