substratum
sub.stra.tum \'s*b-.stra-t-*m, -.strat-, 's*b-'\ \-*\ n or sub.stra.ta [ML,
fr. L, neut. of substratus, pp. of substernere to spread under] pl , fr.
sub- + sternere to spread - more at STREW : an underlying support :
FOUNDATION : as : substance that is a permanent subject of qualities or
phenomena : the material of which something is made and from which it
derives its s pecial qualities : a layer beneath the surface soil; specif :
SUBSOIL : SUBSTRATE, SUBSTRATE : a thin coating (as of hardened gelatin)
on the support of a photographi c film or plate to facilitate the adhesion
of the sensitive emulsion