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, a transistor is located at every photo-sensitive pixel, and reads the pixel value out directly. Often there is a built-in Analog-to-Digital converter built into the sensor, which makes these devices much easier and less expensive to integrate into a camera. However at the current state of technology CMOS sensors have lower sensitivity, higher read noise, and higher dark current than comparable CCD sensors.