Underlying is a synonym of Fundamental. Fundamental is similar to Significant. Significant is related to Importance. 
Period is related to Future. Future is related to Fortune. Fortune is related to Will. 
Underlying <--Synonym--> Fundamental <--SimilarTo--> Significant <--RelatedTo--> Importance 
Period <--RelatedTo--> Future <--RelatedTo--> Fortune <--RelatedTo--> Will 