Come of age
Definition 1 of 3
Pro Tip 1/3Legal Milestone
Used to signify reaching a specific legal age for rights like voting, drinking, or driving. 
She plans to buy her first car when she comes of age.
Pro Tip 2/3Cultural Variations
The legal adult age varies by country; 'come of age' adapts to each nation's laws. 
In many countries, you come of age at 18.
Pro Tip 3/3Ceremonial Use
Often associated with coming-of-age ceremonies or celebrations like Sweet 16, Quinceañera. 
His Bar Mitzvah will celebrate when he comes of age in his community.