( DENSITY ( ( ( tells us ) ( ( how much ) ( matter ( is ( in ( a ( given space ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP DENSITY)) (VP (VBZ tells) (NP (PRP us)) (SBAR (WHADJP (WRB how) (JJ much)) (S (NP (NN matter)) (VP (VBZ is) (PP (IN in) (NP (DT a) (VBN given) (NN space))))))) (. .)))
DENSITY tells us how much matter is in a given space.
(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))))))))) (. .)))