Definition
A sleep disorder marked by persistent difficulty falling asleep, staying asleep, or returning to sleep, resulting in inadequate rest and reduced alertness during waking hours.
Plain English
Trouble sleeping — either not being able to fall asleep, waking up often, or waking too early and not being able to get back to sleep.
Context Anchor
Seen in aeromedical and human factors discussions about fatigue, fitness to fly, and safe pilot decision-making.
Derivation
From Latin 'insomnis' meaning 'sleepless,' from 'in-' (not) + 'somnus' (sleep). The same root appears in 'somnolent' (sleepy). Knowing this helps anchor the word as the opposite of normal sleep.
Why Pilots Care
Unresolved insomnia can disqualify a pilot from holding a valid medical certificate and raises the risk of fatigue-related mistakes.
Grounding Statement
If a pilot lies awake most of the night and reports for an early flight feeling worn out, insomnia may have created a real fatigue risk.
Intuition Check
Insomnia does not just mean choosing to stay up late. It means having trouble sleeping or getting useful rest when you are trying to sleep.
Example Sentence 1
After several nights of insomnia, the pilot grounded himself rather than fly fatigued.
Example Sentence 2
During the preflight briefing the instructor asked about any recent insomnia that might affect alertness.