Timing signal jitter can have a profound impact on a wide variety of applications. Timing signal jitter is generally specified in different ways from one application environment to another. For example, in digital data path synchronization applications, jitter is specified in the time domain as period or cycle-to-cycle jitter. In data communications applications, on the other hand, jitter is specified in the frequency domain as phase noise or “root mean square” (RMS) jitter. This paper provides a basic tutorial on timing signal jitter for designers building electronics systems. It defines the phenomenon and describes how it is measured in different applications.