Complementary Metal Oxide Silicon. A very commonly used type of semiconductor device. In the context of imaging, this refers to a sensor utilizing CMOS technology. In a CMOS sensor, transistors are located at every photo-sensitive pixel, to read the pixel value out directly. Typically there are Analog-to-Digital converters built into the sensor for each column, and sometimes two per column. This makes the CMOS sensors less expensive to build into a camera than CCD sensors, and it also provides for an extremely high readout speed. This can also result in more "amp glow" on the sensor during long exposures.