( ( Interstellar medium ) ( ( is ( ( ( gas and ) dust ) ( that ( occupies ( interstellar space ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Interstellar) (NN medium)) (VP (VBZ is) (NP (NP (NN gas) (CC and) (NN dust)) (SBAR (WHNP (WDT that)) (S (VP (VBZ occupies) (NP (NN interstellar) (NN space))))))) (. .)))
Interstellar medium is gas and dust that occupies interstellar space.
(ROOT (S (NP (JJ Interstellar) (NN medium)) (VP (VBZ consists) (PP (IN of) (NP (NP (RB thinly) (NN spread) (NN gas)) (CC and) (NP (NN dust))))) (. .)))