Age is a synonym of Era. Era is related to Modern. Modern is related to Period. 
Age is related to Iron. Iron is related to Implement. Implement is a type of Device. Device can be used for Purpose. 
Age <--Synonym--> Era <--RelatedTo--> Modern <--RelatedTo--> Period 
Age <--RelatedTo--> Iron <--RelatedTo--> Implement --IsA--> Device --UsedFor--> Purpose 