empty 指空无一人或一物，或空洞无意义的。
vacant 普通用词，侧重某物或某个位置没有被占用。
hollow 指物体中间是空的。
blank 指上面没有写字、印刷或做记号的空白表面，或指上面留着准备被填写的空白处。
open 指未被占有，从而可被别人得到的。
参考例句
1. He hollowed out a cave in the snowfield for night. 他在雪原上挖了个洞以过夜。
2. This is a hollow tree. 这是一棵中空的树。
3. Hollow and alone. 空洞与孤独。
英英解释
n.
1. a cavity or space in something
2. a small valley between mountains
3. a depression hollowed out of solid matter v.
1. remove the inner part or the core of
2. remove the interior of adj.
1. not solid; having a space or gap or cavity
2. deliberately deceptive
3. as if echoing in a hollow space
4. devoid of significance or point
