实体层

physical layer (OSI)

to pile on top of one another / layer; stratum / floor (of a building); story / (math.) sheaf / classifier for layers

body / form / style / system / substance / to experience / aspect (linguistics)

real / true / honest / really / solid / fruit / seed / definitely

entity / substance / thing that has a material existence (as opposed to a conceptual, virtual or online existence) / the real thing (as opposed to an image or model of it)