outer layer
同义词：
external | exterior | outside | outward | extrinsic | out | fringe | peripheral | outlying | remote | over | on the outside | surface | superficial |
反义词：
inner |
outer layer
同义词：
external | exterior | outside | outward | extrinsic | out | fringe | peripheral | outlying | remote | over | on the outside | surface | superficial |
反义词：
inner |