Vacation is related to Trip. Trip is related to Short. Short is related to Shot. Shot is related to Vaccine. 
Classify is a synonym of Class. Class is related to School. School is related to Group. 
Vacation <--RelatedTo--> Trip <--RelatedTo--> Short <--RelatedTo--> Shot <--RelatedTo--> Vaccine 
Classify <--Synonym--> Class <--RelatedTo--> School <--RelatedTo--> Group 