youthful

youthful
youth‧ful /ˈjuːθfəl/ adjective1. typical of young people, or seeming young
    youthful enthusiasm/energy/vigour
    youthful appearance/looks/complexion
    She has managed to maintain her youthful appearance.
2. young:
    The photo shows a smiling, youthful Burgos.
—youthfully adverb
—youthfulness noun [uncountable]
     

THESAURUS

   ▪ young not old: a young man of about 22 | My dad died when I was young. | There are excellent facilities for young children. | Young people are often unable to get jobs.
   ▪ small/little a small child is very young. Little sounds more informal than small, and is used especially in spoken English: They have two small children. | We used to go camping a lot when the kids were little.
   ▪ teenage [only before noun] between the ages of 13 and 19: a group of teenage boys | They have three teenage children.
   ▪ adolescent especially written at the age when you change from being a child into an adult – used especially when talking about the problems that young people have at this age: Sudden mood changes are common in adolescent girls. | adolescent behaviour
   ▪ juvenile /ˈdʒuːvənaɪl $ -nəl, -naɪl/ [only before noun] formal connected with young people who commit crime: juvenile crime | a special prison for juvenile offenders | juvenile deliquents (=young people who commit crimes)
   ▪ youthful especially written seeming young, or typical of someone who is young – often used about someone who is no longer young: a youthful 55 year old | youthful enthusiasm | Andrew still has a slim youthful look about him. | The photograph showed a youthful, smiling Rose.
   ▪ junior connected with sports played by young people rather than adults: the junior championships | the junior champion