Despite his tough exterior, there was a deep tenderness in his voice when he spoke to his daughter.

tenderness 是名词，来自形容词 tender（温柔的、柔软的）加上名词后缀 -ness，表示"温柔、柔软的特性或状态"。这个词常用于描述人的情感或态度，特别是表现出关爱、体贴或同情时的状态。