( ( ( The quantity ) ( of ( space ( an object ) ) ) ) ( ( ( occupies it ) ( ( ( its volume ) , ) ( not mass ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN quantity)) (PP (IN of) (NP (NP (NN space)) (NP (DT an) (NN object))))) (VP (VBZ occupies) (NP (PRP it)) (NP (NP (PRP$ its) (NN volume)) (, ,) (NP (RB not) (JJ mass)))) (. .)))
The quantity of space an object occupies it its volume, not mass.
(ROOT (S (NP (NN Volume)) (VP (VBZ is) (NP (NP (DT a) (NN measure)) (PP (IN of) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN space)))))) (SBAR (IN that) (S (NP (NP (DT a) (NN substance)) (CC or) (NP (DT an) (NN object))) (VP (VBZ occupies))))) (. .)))