Indicator is a synonym of Index. Index is related to Content. 
Age is related to Year. Year is related to Measurement. Measurement is related to Half. Half is the opposite of Birthday. 
Indicator <--Synonym--> Index <--RelatedTo--> Content 
Age <--RelatedTo--> Year <--RelatedTo--> Measurement <--RelatedTo--> Half <--Antonym--> Birthday 