An electronic component that resists the flow of current in an electronic circuit. Resistors are often made out of chunks of carbon or thin films of carbon or other resistive materials. They can also be made of wires wound around a cylinder. The common resistor is a two-wire package with a fixed resistance measured in ohms; however, different types of resistors are adjustable by the circuit designer or the user (see variable resistor).

Discrete or IC
Discrete resistors are individual packages. On a circuit board, discrete axial resistors are commonly used with their two wires soldered into the holes of the board. Generally smaller than axial resistors, discrete surface-mounted resistors are soldered on top of the board. In addition, resistors are built into microprocessors and other integrated circuits (ICs), but they use semiconductor structures for their fabrication in a manner similar to transistors and PN junctions. See variable resistor and thru-hole.