ローム層[roomusou] stratum of loam
亜成層圏[aseisouken] substratosphere
一層[issou] much more
沖積層[chuusekisou] alluvium
下層[kasou] lower strata (classes)

下層階級[kasoukaikyuu] proletariat
下層社会[kasoushakai] the underworld
下層土[kasoudo] subsoil
化石層[kasekisou] fossil bed
階層[kaisou] class

バナナの皮[banananokawa] banana peel
一皮[hitokawa] unmasking
化の皮[bakenokawa] masking one's true character
化けの皮をはぐ[bakenokawawohagu] to unmask (someone's true nature)
果皮[kahi] pericarp (ripened ovary wall forming part of a fruit)

外皮[gaihi] investment (in the sense of outer layer)
角皮[kakuhi] cuticle
桜皮[kanba] birch (esp. Japanese white birch)
乾皮[kanpi] dried hides
雁皮紙[ganpishi] traditional Japanese paper made from the fibre of plant species Diplomorpha sikokiana (high quality, glossy)