Source : WordNet®

pH scale
     n : (chemistry) p(otential of) H(ydrogen); the logarithm of the
         reciprocal of hydrogen-ion concentration in gram atoms
         per liter; provides a measure on a scale from 0 to 14 of
         the acidity or alkalinity of a solution (where 7 is
         neutral and greater than 7 is acidic and less than 7 is
         basic) [syn: {pH}]