( ( ( A ( third property ) ) ( of matter ) ) ( ( is density ) . ) )
(ROOT (S (NP (NP (DT A) (JJ third) (NN property)) (PP (IN of) (NP (NN matter)))) (VP (VBZ is) (NP (NN density))) (. .)))
A third property of matter is density .
(ROOT (S (NP (NP (NNP Density)) (PP (IN of) (NP (NN matter)))) (VP (VBZ reflects) (SBAR (WHADVP (WRB how) (RB closely)) (S (VP (VBD packed) (SBAR (S (NP (NP (DT the) (NNS particles)) (PP (IN of) (NP (NN matter)))) (VP (VBP are)))))))) (. .)))