The opposition, expressed in ohms, offered to the flow of an alternating current by capacitance. The symbol for capacitive reactance is XC.
The opposition to alternating current due to the capacitance of a capacitor, cable, or circuit.(Course Material/EddyCurrents/Instrumentation/impedanceplane.htm)(Course Material/EddyCurrents/Physics/impedance.htm)
in an AC circuit, the voltage across the capacitor divided by the current through the capacitor; analogous to resistance in a DC circuit(see equation 21.18)