Assumption is a type of Hypothesis. Hypothesis is a synonym of Possibility. Possibility is related to Chance. 
Layer is related to Atmosphere. you are likely to find Cloud in/at/on Atmosphere. Cloud is related to Ball. 
Assumption --IsA--> Hypothesis <--Synonym--> Possibility <--RelatedTo--> Chance 
Layer <--RelatedTo--> Atmosphere <--AtLocation-- Cloud <--RelatedTo--> Ball 