substratum
US /səbˈstræt̬.əm/
UK /səbˈstrɑː.təm/
명사
하층
a layer of rock, soil, or similar material that is below another layer:
예시:
•
A substratum of clay kept moisture close to the topsoil.
하층
a layer of rock, soil, or similar material that is below another layer: