puerile

Example:As she grew up, she became more mature in her decisions and actions.

Definition:Fully developed both in physical and mental characteristics; having reached a state of full development; having attained an advanced period of development or growth.

Example:He behaved like a true adult during the family gathering, showing maturity and responsibility.

Definition:Of the adult age; not young; no longer a child or adolescent.

Example:He recently proved his responsibility by dealing with a crisis in a calm and mature manner.

Definition:Having or showing the ability to make judgments or decisions and to be held accountable for one's behavior.