1. The interval of time between the end of a sovereign's reign and the accession of a successor.
2. A period of temporary suspension of the usual functions of government or control.
3. A gap in continuity.
[Latin : inter-, inter- + rgnum, reign]
Despite the etymology, the term can be applied to not only a time period between monarchs, but also that between popes, emperors of the Holy Roman Empire, the pastorates of ministers in some Protestant churches, the period of time between the election of a new President of the United States and his or her inauguration (during which the outgoing president remains in power, but as a lame duck) and the period between the election of a new parliament and the establishment of a new government from that parliament in parliamentary democracies.