reflectivity

n. quality of producing a reflection; quality of being contemplative, state of being pensive; ratio of energy reflected by a surface to the amount of energy striking the surface, reflectance (Physics)

In optics and heat transfer, reflectivity is the fraction of incident radiation reflected by a surface. In full generality it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength. However it is also common averaged over the reflected hemisphere as follows
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Noun
1. the fraction of radiant energy that is reflected from a surface
(synonym) coefficient of reflection, reflection factor, reflectance
(hypernym) coefficient
2. the ability to reflect beams or rays
(synonym) reflection, reflexion
(hypernym) physical property
(hyponym) echo, reverberation, sound reflection, replication

The reflectance at the surface of a material so thick that the reflectance does not change with increasing thickness, i.e., the intrinsic reflectance of the surface, irrespective of other parameters such as the reflectance of the rear surface. Note: The term "reflectivity" is no longer in common use. See reflectance.

Radar term referring to the ability of a radar target to return energy; used to derive echo intensity, and to estimate precipitation intensity and rainfall rates. See dBZ VIP .