youthfulness

n.the freshness and vitality characteristic of a young person

同义词：youthjuvenility

1. Her youthfulness is evident in her bright smile and energetic personality.
   她的年轻气质在她灿烂的微笑和充满活力的个性中展现无遗。
2. Despite his age, he still maintains a remarkable youthfulness.
   尽管年纪已大，他依然保持着惊人的青春气息。