admittance Symbol, Y. Unit, siemens (formerly
mho). The property denoting the comparative
ease with which an alternating current flows
through a circuit or device. Admittance is the reciprocal
of impedance (Z ): Y = 1/Z.
adp 1. Abbreviation of AMMONIUM DIHYDROGEN
PHOSPHATE, a piezoelectric compound used for
sonar crystals. 2. Abbreviation of AUTOMATIC
adsorption Adhesion of a thin layer of molecules of
one substance to the surface of another without
absorption. An example is adsorption of water to
the surface of a dielectric. This term is often confused
with ABSORPTION because the spellings of
the two words are almost identical. Compare ABSORPTION....