1. A single series of interconnected devices through which data can flow from source to recorder. Seismic systems may have thousands of channels allowing the simultaneous recording of energy from thousands of geophone groups. 2. A measured or computed quantity that occurs as a sequence of samples indexed against time, depth, or some other physical dimension. 3. A localized elongated geologic feature resulting from drainage or water action. The properties of the material in-filling a channel often differ from those of the material into which the channel is cut, which makes the channel observable and sometimes bends raypaths creating dip and/or velocity anomalies in underlying reflections. 4. A feature in seismic data that is interpreted as indicating erosion and fill by a river system, such as a curvilinear feature on a 3-D horizon slice (see Figure H-8). 5. An allocated portion of the radio-frequency spectrum. 6. A time gate during which measurements are made in time-domain electromagnetic surveying. Measurements made during several time gates following a source pulse yield several channels of data. 7. A layer whose velocity is such that seismic energy gets trapped; see channel wave. 8. A gate with upper and lower energy thresholds followed by a count rate meter, used in gamma-ray spectrometers. 9. A component of a mainframe processor that supports and controls I/O.