( Voltage ( ( is ( ( the measure ) ( of ( electric potential ) ) ) ) . ) )
(ROOT (S (NP (NNP Voltage)) (VP (VBZ is) (NP (NP (DT the) (NN measure)) (PP (IN of) (NP (JJ electric) (NN potential))))) (. .)))
Voltage is the measure of electric potential.
(ROOT (S (NP (PRP We)) (VP (VBP use) (ADJP (JJ voltage) (S (VP (TO to) (VP (VB keep) (NP (NP (NN track)) (PP (IN of) (NP (JJ electric) (JJ potential) (NN energy))))))))) (. .)))
We use voltage to keep track of electric potential energy.