( ( Since ( they ( are gases ) ) ) ( , ( they ( ( have ( no ( definite ( ( shape or ) volume ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Since) (S (NP (PRP they)) (VP (VBP are) (NP (NNS gases))))) (, ,) (NP (PRP they)) (VP (VBP have) (NP (DT no) (JJ definite) (NN shape) (CC or) (NN volume))) (. .)))
Since they are gases, they have no definite shape or volume.
(ROOT (S (NP (NNP Gas)) (VP (VBZ has) (NP (NP (DT no) (JJ definite) (NN volume)) (CC and) (NP (DT no) (JJ definite) (NN shape)))) (. .)))
Gas has no definite volume and no definite shape.