Vigour and excitement are the prime characteristics of youth.

Solution (By Examveda Team)

Youth : the period between childhood and adult age.
Adolescence : the period following the onset of puberty during which a young person develops from a child into an adult.
Teenage : denoting a person between 13 and 19 years old.
Childhood : the state or period of being a child.
Senility : old age.

Antonym of Youth is Senility