Capacitors, often referred to simply by their ability to hold an electric charge as capacitance, are denoted by the letter C. Definition 1: A capacitor, as the name implies, is 'a container for electricity', a device that holds an electric charge. English name: capacitor. capacitor is one of the electronic components used in a large number of electronic devices, widely used in circuit isolation through the cross, coupling, bypass, filtering, tuning circuit, energy conversion, control, etc.. Definition 2: Capacitor, any two conductors (including wires) that are insulated from each other and close together constitute a capacitor.