a physical emptiness, like a cavity within something, or it can be used metaphorically to describe a lack of substance, sincerity, or meaning in something or someone.
noun [抽象名词]空泛,空虚
Feel the hollowness inside of your heart. 感受到你内心的空虚。
hollowness
“ -ness” ⌜ 表示状态或质量的性质 - indicating the state or quality of ~ ⌟