( ( ( ( Alternating Current ) ( -LRB- ( AC -RRB- ) ) ) ( ( An ( electric current ) ) ( that ( periodically ( reverses ( direction ( of ( electron flow ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (NP (VBG Alternating) (NNS Current)) (PRN (-LRB- -LRB-) (NP (NNP AC)) (-RRB- -RRB-))) (NP (NP (DT An) (JJ electric) (NN current)) (SBAR (WHNP (WDT that)) (S (ADVP (RB periodically)) (VP (VBZ reverses) (NP (NP (NN direction)) (PP (IN of) (NP (NN electron) (NN flow)))))))) (. .)))
Alternating Current (AC) An electric current that periodically reverses direction of electron flow.
(ROOT (S (NP (VBG Alternating) (NN current)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (JJ electric) (NN current))) (SBAR (WHNP (WDT that)) (S (VP (VBZ keeps) (S (VP (VBG reversing) (NP (NN direction))))))))) (. .)))