( ( pH ( ( A measure ) ( of ( the ( hydrogen-ion activity ) ) ) ) ) ( ( in ( a solution ) ) ( , ( ( ( ( ( expressed ( as ( ( the ( negative log10 ) ) ( of ( hydrogen ( ion concentration ) ) ) ) ) ) ( on ( ( a scale ) ( of 0 ) ) ) ) ( -LRB- ( ( highly acidic ) -RRB- ) ) ) ( ( to ( 14 ( -LRB- ( ( highly basic ) -RRB- ) ) ) ) ( with ( ( ( a pH ) ( of 7 ) ) ( being neutral ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN pH) (NP (NP (DT A) (NN measure)) (PP (IN of) (NP (DT the) (JJ hydrogen-ion) (NN activity))))) (PP (IN in) (NP (DT a) (NN solution))) (, ,) (VP (VBD expressed) (PP (IN as) (NP (NP (DT the) (JJ negative) (NN log10)) (PP (IN of) (NP (NN hydrogen) (NN ion) (NN concentration))))) (PP (IN on) (NP (NP (DT a) (NN scale)) (PP (IN of) (NP (CD 0))))) (PRN (-LRB- -LRB-) (ADJP (RB highly) (VBN acidic)) (-RRB- -RRB-)) (PP (TO to) (NP (NP (CD 14)) (PRN (-LRB- -LRB-) (ADJP (RB highly) (JJ basic)) (-RRB- -RRB-))) (PP (IN with) (S (NP (NP (DT a) (NN pH)) (PP (IN of) (NP (CD 7)))) (VP (VBG being) (ADJP (JJ neutral))))))) (. .)))
pH A measure of the hydrogen-ion activity in a solution, expressed as the negative log10 of hydrogen ion concentration on a scale of 0 (highly acidic) to 14 (highly basic) with a pH of 7  being neutral.
(ROOT (S (NP (DT The) (NN ph) (NN scale)) (VP (VP (VBZ measures) (NP (NNS acids) (CC and) (NNS bases))) (CC and) (VP (VBZ has) (NP (NP (CD 7)) (PP (IN as) (NP (DT a) (JJ neutral) (NN value)))))) (. .)))
The ph scale measures acids and bases and has 7 as a neutral value.