( ( ( The density ) ( of ( an object ) ) ) ( ( is ( ( the amount ) ( of ( matter ( ( packed ( into ( the space ) ) ) ( that ( object fills ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN density)) (PP (IN of) (NP (DT an) (NN object)))) (VP (VBZ is) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN matter)) (VP (VBN packed) (PP (IN into) (NP (DT the) (NN space))) (SBAR (IN that) (S (NP (NN object)) (VP (VBZ fills))))))))) (. .)))
The density of an object is the amount of matter packed into the space that object fills.
(ROOT (S (NP (NNP Density)) (VP (VBZ describes) (SBAR (WHADJP (WRB how) (JJ much)) (S (NP (NN matter)) (VP (VBZ is) (PP (IN in) (NP (NP (DT a) (JJ certain) (NN amount)) (PP (IN of) (NP (NN space))))))))) (. .)))