The vivacious child's laughter and energy filled the entire room during the party.

vivacious 由拉丁词根 viv-（生命、活力）和后缀 -acious（充满...的）组成，字面意思是"充满生命力的"。这个词形容人性格活泼开朗、精力充沛，通常带有积极正面的含义。