( ( The period ) ( ( ( is simply ) ( ( the reciprocal ) ( of ( the frequency ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN period)) (VP (VBZ is) (ADVP (RB simply)) (NP (NP (DT the) (NN reciprocal)) (PP (IN of) (NP (DT the) (NN frequency))))) (. .)))
The period is simply the reciprocal of the frequency.
(ROOT (S (NP (NP (DT The) (NN frequency)) (PP (IN of) (NP (DT a) (NN wave)))) (VP (VBZ is) (NP (NP (DT the) (NN reciprocal)) (PP (IN of) (NP (NP (DT the) (NN period)) (PP (IN of) (NP (DT the) (NN wave))))))) (. .)))