( ( ( Pupil -- ) ( ( ( the opening ) ( in ( your eye ) ) ) ( that ( allows ( light ( to enter ) ) ) ) ) ) . )
(ROOT (NP (NP (NNP Pupil)) (: --) (NP (NP (DT the) (NN opening)) (PP (IN in) (NP (PRP$ your) (NN eye))) (SBAR (WHNP (WDT that)) (S (VP (VBZ allows) (ADJP (JJ light) (S (VP (TO to) (VP (VB enter))))))))) (. .)))
Pupil -- the opening in your eye that allows light to enter.
(ROOT (S (NP (NP (DT The) (NN pupil)) (PP (IN of) (NP (DT the) (NN eye)))) (VP (VBZ allows) (ADJP (JJ light) (S (VP (TO to) (VP (VB enter)))))) (. .)))
The pupil of the eye allows light to enter.