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

ストックホルム症候群[sutokkuhorumushoukougun] Stockholm syndrome
亜群[agun] subgroup
一群[ichigun] group
一群れ[hitomure] group
可換群[kakangun] Abelian group

魚群[gyogun] school of fish
繰込み群[kurikomigun] renormalisation group (physics)
群がる[muragaru] to swarm
群れ[mure] group