n.
   - an event or a sequence of events. ▸a finite period in which someone is affected by an illness. 
- each of the instalments into which a serialized story or radio or television programme is divided.
- Music  a passage containing distinct material or introducing a new subject. ▸a section between two choric songs in Greek tragedy. 
Etymology
  C17: from Gk epeisodion, neut. of epeisodios ‘coming in besides’.