Sub*stra"tum (?), n.; pl. Substrata (#). [L. substratus, p.p. of substernere to strew under; sub under + sternere to strew. See Stratum.]
That which is laid or spread under; that which underlies something, as a layer of earth lying under another; specifically Agric., the subsoil.
The permanent subject of qualities or cause of phenomena; substance.
© Webster 1913.