ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables. pH pH is the measure of the acidity or alkalinity of a solution. pH is formally a measure of the activity of dissolved hydrogen ions (H+). Solutions in which the concentration of H+ exceeds that of OH- have a pH value lower than 7.0 and are known as acids. Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV.