something that is null (especially an enactment that has no legal validity)
nullity详细解释
nul.li.ty n.（名词）【复数】nul.li.ties The state or quality of being null.无效：无效的状况或性质Something that is null, especially an act having no legal validity.无效：无效的东西，尤指无法律效力的法案
