youth·ful 
/ˈju:θfəl/ adjective
/ˈju:θfəl/ adjective [more youthful; most youthful] 1 : having or showing the freshness or energy of someone who is young
▪ youthful good looks ▪ He's a youthful 50-year-old. ▪ My grandparents are still very youthful. 2 : having or showing the innocence, hope, lack of knowledge, etc., of someone who is young
▪ youthful optimism ▪ youthful inexperience
▪ youthful good looks ▪ He's a youthful 50-year-old. ▪ My grandparents are still very youthful.
▪ youthful optimism ▪ youthful inexperience
— youth·ful·ly adverb
▪ a youthfully energetic group
▪ a youthfully energetic group
— youth·ful·ness noun [noncount]
