( They ( ( have ( measured ( ( ( volume or ) ( ( the amount ) ( of ( space matter ) ) ) ) ( takes up ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP have) (VP (VBN measured) (SBAR (S (NP (NP (NN volume)) (CC or) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN space) (NN matter))))) (VP (VBZ takes) (PRT (RP up))))))) (. .)))
They have measured volume or the amount of space matter takes up.
(ROOT (S (NP (DT The) (NN term) (NN volume)) (VP (VBZ means) (SBAR (S (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN space) (NN matter)))) (VP (VBZ takes) (PRT (RP up)))))) (. .)))