n. difficulty in initiating or maintaining a restorative sleep, which results in fatigue, the severity or persistence of which causes clinically significant distress or impairment in functioning. Such sleeplessness may be caused by a transient or chronic physical condition or psychological disturbance. Also called agrypnia; ahypnia; ahypnosia; anhypnia. See disorders of initiating and maintaining sleep; fatal familial insomnia; initial insomnia; intermittent insomnia; middle insomnia; primary insomnia; pseudoinsomnia; terminal insomnia. —insomniac n.

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May 1st 2024

pia-arachnoid

n. the inner two coverings of the brain and spinal cord—the pia mater and arachnoid mater—considered as a single structure. See meninges.