[en] Radiation effects is an interdisciplinary subject which contains radiological physics and solid-state physics at its core. The radiation effects which are of concern here occur predominantly in solids and require considerable appreciation of solid-state physics. The need for this understanding arose as a matter of urgency only in the late 1950's when semiconductor technology began to be used in space and military equipment. This first chapter gives a brief review of radiological physics, units, and measurement methods