Serious is related to Disease. Disease is related to Severe. Severe is a synonym of Bad. Bad is related to Bitter. 
Stretch is related to Length. Length is related to Far. Far is related to Perspective. 
Serious <--RelatedTo--> Disease <--RelatedTo--> Severe <--Synonym--> Bad <--RelatedTo--> Bitter 
Stretch <--RelatedTo--> Length <--RelatedTo--> Far <--RelatedTo--> Perspective 