IEC TR 63039:2016(E) provides guidance on probabilistic risk analysis (hereafter referred to as risk analysis) for the systems composed of electrotechnical items and is applicable (but not limited) to all electrotechnical industries where risk analyses are performed. This document deals with the following topics from the perspective of risk analysis: - defining the essential terms and concepts; - specifying the types of events; - classifying the occurrences of events; - describing the usage of modified symbols and methods of graphical representation for ETA, FTA and Markov techniques for applying those modified techniques complementarily to the complex systems; - suggesting ways to handle the event frequency/rate of complex systems; - suggesting ways to estimate the event frequency/rate based on risk monitoring; - providing illustrative and practical examples. Please refer to the Introduction and Scope of the document for addition information regarding the events covered by and associated risks. This document defines the basic properties of events from the perspective of probabilistic risk analysis and use of dependability-related techniques for the analysis of occurrence of the final event that results in a final state in which the final consequences of a risk may appear. Keywords: probabilistic risk analysis, effects of uncertainty, events and associated risks