大般涅槃經義記 6.7

6.7

就前八中，初七明其眾生及法無性故空，後一明其眾生及法無相故空。因緣假中而無定性名無性空，畢竟空中無因緣相名無相空。

Within the first eight: the first seven clarify that sentient beings and dharmas are empty because they lack intrinsic nature; the last one clarifies that sentient beings and dharmas are empty because they lack marks. Within conditional nominality, lacking a fixed nature is called emptiness of non-nature; within ultimate emptiness, lacking the marks of causes and conditions is called markless emptiness.