( ( ( the amount ) ( of ( matter ( in ( the universe ) ) ) ) ) ( , ( ( called ( the ( density parameter ) ) ) ; ) ) )
(ROOT (S (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN matter)) (PP (IN in) (NP (DT the) (NN universe)))))) (, ,) (VP (VBD called) (NP (DT the) (NN density) (NN parameter))) (: ;)))
the amount of matter in the universe, called the density parameter;
(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))))))))) (. .)))