1. (n.) That which is laid or spread under; that which underlies something, as a layer of earth lying under another; specifically (Agric.), the subsoil.

2. (n.) The permanent subject of qualities or cause of phenomena; substance.

air atom atomic particles band base basement basis bearing wall bed bedding bedrock belly belt bottom bottom side breech brute matter building block buttocks chemical element component constituent core couche course deck downside earth element elementary particle elementary unit fire floor flooring fond footing foundation fundament fundamental fundamental particle gallery ground grounds groundwork hardpan hyle hypostasis infrastructure layer ledge level lower side lowest layer lowest level material material world materiality matter measures meat molecule monad natural world nature nether side nethermost level overlayer overstory pavement physical world plenum principle radical riprap rock bottom root rudiment seam seat shelf sill solid ground solid rock stage step stereobate story stratum stuff stylobate substance substrate substruction substructure superstratum terra firma the four elements thickness tier topsoil underbelly underbuilding undercarriage undergirding underlayer underneath underpinning underside understory understratum understruction understructure unit of being water zone