The use of equipment that causes and is susceptible to various electromagnetic phenomena has heightened the interest in power quality. An increase in operational problems has led to a variety of attempts to describe the phenomena. Because different segments of the technical community have used different terminologies to describe these electromagnetic events, this recommended practice provides users with a consistent set of terms and definitions for describing these events. An understanding of how power quality events impact the power system and end-use equipment is required in order to make monitoring useful. Proper measuring techniques are required to safely obtain useful, accurate data. Appropriate location of monitors, systematic studies, and interpretation of results will enhance the value of power quality monitoring. The purpose of this recommended practice is to assist users as well as equipment and software manufacturers and vendors by describing techniques for defining, measuring, quantifying, and interpreting electromagnetic disturbances on the power system.