( ( ( ( ( Both ( have ( a ( definite shape ) ) ) ) , ) but ) ( ( only gases ) ( have ( a ( definite volume ) ) ) ) ) . )
(ROOT (S (S (NP (DT Both)) (VP (VBP have) (NP (DT a) (JJ definite) (NN shape)))) (, ,) (CC but) (S (NP (JJ only) (NNS gases)) (VP (VBP have) (NP (DT a) (JJ definite) (NN volume)))) (. .)))
Both have a definite shape, but only gases have a definite 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.