an inability to sleep; chronic sleeplessness
"After months of insomnia, she finally saw a doctor to help her overcome her chronic sleeplessness."
A sleeping disorder that is known for its symptoms of unrest and the inability to sleep.
"Chronic insomnia left her tossing and turning in restless agitation all night long without finding any relief."
In plain English: Insomnia is when you have trouble falling asleep or staying asleep even though you are tired.
"She struggled with insomnia for months before finding relief through better sleep hygiene habits."
Usage: Use this term specifically when referring to chronic difficulty falling or staying asleep, rather than a single night of poor rest which might be described as "sleeplessness." It often appears in formal medical contexts but can also describe personal struggles with nightly wakefulness.
The word insomnia comes directly from the Latin phrase insomnia, which combines "in-" meaning without and "somnus" meaning sleep. It entered English with its current sense of being unable to sleep rather than referring to a lack of dreams as it originally did in classical usage.