Sub‐stra″tum (?), n.; pl.Substrata (#). [L. substratus, p. p. of substernere to strew under; sub under + sternere to strew. See Stratum.] 1. That which is laid or spread under; that which underlies something, as a layer of earth lying under another; specifically (Agric.), the subsoil.
2. (Metaph.) The permanent subject of qualities or cause of phenomena; substance.