Definition - What does System Unit mean? A system unit is the part of a computer that houses the primary devices that perform operations and produce results for complex calculations. It includes the motherboard, CPU, RAM and other components, as well as the case in which these devices are housed. This unit performs the majority of the functions that a computer is required to do.
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)
the extent or amount of space between two things, points, lines, etc. 2. the state or fact of being apart in space, as of one thing from another; remoteness. 3. a linear extent of space: Seven miles is a distance too great to walk in an hour. 4. an expanse; area: A vast distance of water surrounded the ship. 5. the interval between two points of time; an extent of time: His vacation period was a good distance away.