Of Age

The term being of age is, quite obviously, not an easy one on Turian, just by looking at the multitude of varying species, races and cultures it must be obvious that this term should apply with a plethora of different meanings. However, it does not. Another indicator of a unifying influence all throughout Turian.
from Turian's inconsistencies. An argument for the creation theory

The term "Of Age" is commonly revered as "old enough" to be considered a full-fledged member of society. To be reasonable and responsible to the same degree as any other full member.
In general terms, this includes the duties and privileges of the status. Depending on various cultural habits and traditions this could include compulsory labour, conscription and other services but is generally compensated for by lawful protection, rights of freedom or the ability to own stuff and various other boons. The cultures are differing in that regard massively.

The term "Of Age" is a binding and lawful designation thusly it is regulated by the laws of the land and culture.