( ( ( alternating ( current ( -LRB- ( AC -RRB- ) ) ) ) ( ( An ( electric current ) ) ( that ( reverses ( direction ( in ( a ( periodic manner ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (RB alternating) (JJ current) (PRN (-LRB- -LRB-) (NP (NNP AC)) (-RRB- -RRB-))) (NP (NP (DT An) (JJ electric) (NN current)) (SBAR (WHNP (WDT that)) (S (VP (VBZ reverses) (NP (NP (NN direction)) (PP (IN in) (NP (DT a) (JJ periodic) (NN manner)))))))) (. .)))
alternating current (AC) An electric current that reverses direction in a periodic manner.
(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))))))))) (. .)))