noun
youthfulness; juvenility
The quality or state of being youthful, fresh, or energetic, often in appearance or spirit.
彼女の若々しさは年齢を感じさせない。
Her youthfulness makes her age hard to guess.
この化粧品は肌の若々しさを保つ効果がある。
This cosmetic product helps maintain the youthfulness of the skin.
Derived from the adjective 若々しい (youthful) by adding the nominalizing suffix さ, which turns an adjective into a noun expressing degree or quality.