The root word of youthful is youth.
Breakdown:
- Youth is the base word, meaning the early stage of life or the period between childhood and adulthood.
- -ful is a suffix meaning “full of” or “having the qualities of,” turning “youth” into an adjective that describes being full of youth or youthful qualities.
Thus, youthful refers to being young, energetic, or exhibiting youthful characteristics.