( ( A wavelength ) ( ( is ( ( the distance ) ( between ( ( ( two ( adjacent troughs ) ) or ) crests ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN wavelength)) (VP (VBZ is) (NP (NP (DT the) (NN distance)) (PP (IN between) (NP (NP (CD two) (JJ adjacent) (NNS troughs)) (CC or) (NP (NNS crests)))))) (. .)))
A wavelength is the distance between two adjacent troughs or crests.
(ROOT (S (NP (NNP Wavelength)) (VP (VBZ is) (NP (NP (DT the) (NN distance)) (PP (IN between) (NP (NP (CD two) (JJ corresponding) (NNS points)) (PP (IN of) (NP (NP (JJ adjacent) (NNS waves)) (VP (VBN called)))))))) (. .)))
Wavelength is the distance between two corresponding points of adjacent waves called.