IPA: /ˈjuːθfəl/
KK: /ˈjuːθfəl/
Having the qualities or characteristics of being young; energetic and fresh.
She has a youthful spirit that makes her fun to be around.
Comparative: more youthful
Superlative: most youthful
Youthful → It is formed from "youth" (from Old English *geogð*, meaning the period of being young) and "-ful" (meaning full of). The word "youthful" means full of youth or characteristics associated with being young.
Think of 'youth' as the time of being young, and '-ful' means full of something. So, youthful describes someone who is full of the qualities of youth.