unchangeability, unchangeableness, unchangingness, changelessness - the quality of being unchangeable; having a marked tendency to remain unchanged

metastability - the quality of a physical system that persists in its existing equilibrium when undisturbed (or only slightly disturbed) but able to pass to a more stable equilibrium when sufficiently disturbed

monotony - constancy of tone or pitch or inflection

perception - the process of perceiving

brightness constancy - the tendency for a visual object to be perceived as having the same brightness under widely different conditions of illumination

color constancy, colour constancy - the tendency for a color to look the same under widely different viewing conditions

shape constancy - the tendency to perceive the shape of a rigid object as constant despite differences in the viewing angle (and consequent differences in the shape of the pattern projected on the retina of the eye)

size constancy - the tendency to perceive the veridical size of a familiar object despite differences in their distance (and consequent differences in the size of the pattern projected on the retina of the eye)

faithfulness, fidelity - the quality of being faithful