interregnum
A period of time between the end of one monarch's reign and the accession of their successor.
The Sasanian Interregnum of 628–632
A break in continuity; a gap, an intermission.
figuratively
Is it not Pelham who wonders what becomes of servants when they are not wanted;—whether, like the tones of an instrument, they exist but when called for? About servants we will not decide; but that some such interregnum certainly occurs in female existence on rising from table, no one can doubt who ever noted the sound of the dining and the silence of the drawing-room.
A period of time between when a minister or pastor leaves a church and when a new one is installed.
A period of time between the end of one political leader's term and the start of the term of their successor; a period of time during which normal executive leadership is interrupted or suspended, and a polity is either left without leadership or has only a temporary one.
Darker questions still emerge in these dusky final weeks of our interregnum.
Where it comes from
Learned borrowing from Latin interrēgnum, from inter- (prefix meaning ‘between’) (ultimately from Proto-Indo-European *h₁entér (“between”)) + rēgnum (“reign; royal power”) (nominalized from the neuter of *rēgnus, from rēx (“king; ruler”, oblique stem rēg-) + -nus (suffix forming adjectives), ultimately from Proto-Indo-European *h₃reǵ- (“to righten; to straighten”)). The plural form interregna is a learned borrowing from Latin interrēgna.
Adapted from the Wiktionary entry interregnum (CC BY-SA 4.0).