pH stands as a very important concept in pharmacy and pharmaceutical sciences .This booklet is not adding any new ideas or concepts to the already existing knowledge about the pH, but it is an attempt to collect the existing information about pH from different sources and put them in one place to make them handy for the scientists in different disciplines of pharmaceutical science.The first part of the book covers, the basic theoretical and basic concepts of pH. The rest of the chapters are dedicated to the importance and application of pH in the different disciplines of pharmaceutical sciences.