Final answer:
In the novel 'Illuminae,' First Lieutenant Zhenya's callsign is 'Cyclone.' Callsigns are important in the military for identification and efficient communication.
Step-by-step explanation:
In the science fiction novel Illuminae by Amie Kaufman and Jay Kristoff, First Lieutenant Zhenya’s callsign is Cyclone. This detail is a part of the character development and world-building within the narrative, contributing to the rich tapestry of the book's military and space opera elements.
Callsigns in military contexts often serve as a form of identification used during operations and missions, providing anonymity and brevity in communication.