( ( ( Concave Lens ) ( A ( concave lens ) ) ) ( ( is ( ( the opposite ) ( of ( a ( convex lens ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Concave) (NNP Lens)) (NP (DT A) (JJ concave) (NN lens))) (VP (VBZ is) (NP (NP (DT the) (NN opposite)) (PP (IN of) (NP (DT a) (NN convex) (NN lens))))) (. .)))
Concave Lens A concave lens is the opposite of a convex lens.
(ROOT (S (NP (JJ Concave) (NNS lenses)) (VP (MD can) (VP (VB correct) (NP (NN myopia)))) (. .)))