The reduction in the apparent brightness of a celestial object due to absorption and scattering of its light by the atmosphere and by interstellar dust; it is greater at low altitudes.

The worldwide death and disappearance of a specific organism or group of organisms.

The drying up of lake by either water loss or destruction of the lake basin.

Phenomenon in which plane polarized light is almost completely absorbed by a polarizer whose axis is perpendicular to the plane of polarization.

See <<absorbance>>

Decrease in frequency and elimination of a conditioned response if reinforcement of the response is withheld.