insomnia

This term describes a clinical or persistent state of sleep deprivation rather than a one-off sleepless night. It carries a medical connotation, often implying a chronic condition that disrupts daily functioning and mental well-being, distinguishing it from simple restlessness.

As an uncountable noun, insomnia cannot be pluralized or counted with numbers. To refer to specific instances or types of the condition, speakers must use partitive constructions such as a bout of insomnia or a case of insomnia.