( Density ( ( is ( ( a measurement ) ( of ( ( how much ) ( matter ( is ( packed ( into ( a ( certain volume ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Density)) (VP (VBZ is) (NP (NP (DT a) (NN measurement)) (PP (IN of) (SBAR (WHADJP (WRB how) (JJ much)) (S (NP (NN matter)) (VP (VBZ is) (VP (VBN packed) (PP (IN into) (NP (DT a) (JJ certain) (NN volume)))))))))) (. .)))
Density is a measurement of how much matter is packed into a certain volume.
(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))))))))) (. .)))