ab·sorb·en·cy \ ̷ ̷ˈ ̷ ̷bənsē, -si\noun (-es) 1.: the quality or state of being absorbent 2.orab·sorb·ance\-ən(t)s\orab·sorb·an·cy\-ənsē, -si\: the ability of a layer of a substance to absorb radiation expressed mathematically as the negative common logarithm of transmittance — compare absorptance