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)
Size is the magnitude or dimensions of a thing, or how big something is. Size can be measured as length, width, height, diameter, perimeter, area, volume, or mass. This animation gives a sense of the awe-inspiring scale of some of the known objects in our universe. In mathematical terms, size is a concept abstracted from the process of measuring by comparing a longer to a shorter. Size is determined by the process of comparing or measuring objects, which results in the determination of the magnitude of a quantity, such as length or mass, relative to a unit of measurement.