Reactance is represented by the letter X and is expressed in terms of ohms.
Reactance is the "opposition" to alternating current in a circuit.
This opposition is caused by both inductance and capacitance, therefore there is inductive reactance, capacitive reactance and, of course, plain reactance.
Let's look at their formulas.
Inductive Reactance (XL) = 2 π x Frequency (F) x Inductance (L)
XL = 6.28 x F x L
Capacitive Reactance (Xc) = 1/2 π x Frequency (F) x Capacitance(C)
Xc = 1/6.28 x F x C
Reactance (X) = Capacitive Reactance (Xc) - Inductive Reactance (XL)