IPA: /ˈhɒlənəs/
KK: /ˈhɑloʊnəs/
The condition of having an empty space inside something, making it not solid.
The hollowness of the tree trunk made it easy for animals to live inside.
Hollowness → It is formed from "hollow" (from Old English *holh*, meaning a hole or cavity) and "-ness" (meaning the state or quality of). The word "hollowness" refers to the state of being hollow or having a cavity.
Think of 'hollow' as describing something with a 'hole' or 'cavity' and '-ness' indicating a state, so hollowness means the state of being hollow.