non·age 
(nŏnĭj, nōnĭj)
(nŏnĭj, nōnĭj)n.
1. The state or condition of being under legal age.
2. The period during which one is under legal age.
3. A period of immaturity: "The bravest achievements were always accomplished in the nonage of a nation" (Thomas Paine).
[Middle English nounage, from Anglo-Norman, variant of Old French nonaage : non-, non- + aage, age; see AGE.]