In electronics, a generic name for miniature components that are entirely mounted to the surface of a circuit board. Historically electronic components had little legs, called leads, that protruded through holes in the circuit board. Solder was applied from the backside to hold them in place and make electrical connection. As electronic parts became smaller and smaller it became more efficient to just mount the component to the front surface of the circuit. These components usually rest entirely on the circuit board with contacts at the leads on the component soldered directly to the top of the board. Besides making things more compact, it also makes it even easier for modern machinery to build high-density circuits with more efficiency, thus lowering the price of equipment to the end user. The only downside to SM components is that they are harder to replace in the field. Precision soldering/desoldering equipment and a very steady hand is required. Often a magnifying lens must be used. Most electronic equipment you buy today is made predominantly with surface mount components.