[ in-som-nee-uh ]
/ ɪnˈsɒm ni ə /
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See synonyms for: insomnia / insomnious on Thesaurus.com

inability to obtain sufficient sleep, especially when chronic; difficulty in falling or staying asleep; sleeplessness.
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Origin of insomnia

1685–95; <Latin, equivalent to insomn(is) sleepless (in-in-3 + somn(us) sleep + -is adj. suffix) + -ia-ia


in·som·ni·ous, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What does insomnia mean?

Insomnia is the inability to fall asleep or stay asleep for an adequate amount of time.

Insomnia is often used casually to refer to occasional sleeplessness or a single instance of it. But in medical terms, insomnia typically refers to a condition involving a chronic inability to fall or stay asleep, meaning the inability is persistent and prolonged—it happens all the time.

A person who experiences insomnia can be called an insomniac.

Example: My insomnia gets worse when I’m under a lot of stress.

Where does insomnia come from?

The first records of insomnia come from the 1600s. It comes from the Latin insom(nis), meaning “without sleep.” This is formed from the prefix in, in this case meaning “not,” the root somn(us), meaning “sleep,” and the ending -ia, which is used in the names of diseases.

Insomnia is the most common sleep disorder—around a third of adults may experience it at some point in their lives. It can be acute (lasting one night to a few weeks) or chronic (three or more nights a week for three months or more). Some cases of insomnia are labeled as primary, meaning they’re not caused by another medical condition. Those that are caused by another medical condition are called secondary. Primary insomnia is very often caused by things like stress, changes in sleep schedule, or an environment that’s not good for sleeping (like a room that’s too loud or bright). For instance, the worry and stress that can come with a major life change can cause acute primary insomnia. Secondary insomnia can be caused by things like anxiety, depression, asthma, and sleep apnea (a condition in which a person repeatedly stops breathing and starts again during sleep).

Clinically speaking, insomnia usually refers to sleeplessness so bad that it regularly disrupts a person’s daily life with problems like fatigue and inability to concentrate. Still, the word is commonly used when talking about minor difficulties in falling asleep, as in I was so excited about the trip that I had insomnia last night—it took me an hour to fall asleep!

In general, a sleep dysfunction like insomnia is called a parasomnia, and the names of many of these disorders are based on the same root word, including somnambulism (sleepwalking) and hypersomnia (excessive sleeping).

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How is insomnia used in real life?

Insomnia is a medical term that refers to chronic sleeplessness, but it is also commonly used in a casual way to refer to not being able to fall asleep in any situation.



Try using insomnia!

Is insomnia used correctly in the following sentence? 

I always wake up feeling refreshed after a full night of insomnia.

How to use insomnia in a sentence

British Dictionary definitions for insomnia

/ (ɪnˈsɒmnɪə) /

chronic inability to fall asleep or to enjoy uninterrupted sleepRelated adjective: agrypnotic

Derived forms of insomnia

insomnious, adjective

Word Origin for insomnia

C18: from Latin, from insomnis sleepless, from somnus sleep
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for insomnia

[ ĭn-sŏmnē-ə ]

Chronic inability to fall asleep or remain asleep for an adequate length of time.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for insomnia

[ (in-som-nee-uh) ]

A persistent and prolonged inability to sleep.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.