( ( Convex ( lens lab ) ) . )
(ROOT (NP (NP (NNP Convex)) (NP (NN lens) (NN lab)) (. .)))
Convex lens lab.
(ROOT (S (NP (NP (DT The) (NN lens)) (PP (IN of) (NP (DT the) (NN eye)))) (VP (VBZ is) (S (NP (DT a) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN convex)) (VP (VB shape)))) (. .)))