What does sleepless mean?
Sleepless means unable to sleep or unable to remain asleep, and it can also characterize a period of prolonged wakefulness. The word may describe a temporary condition, as in “a sleepless night,” or a recurring experience associated with worry, illness, stress, or other causes. Because sleeplessness often implies discomfort, fatigue, and continued alertness, the adjective can carry a weary or uneasy emotional tone even when no specific cause is given. It is common in both British and American English and works in everyday conversation as well as in formal writing. The related noun “sleeplessness” is especially useful when discussing the condition itself, its causes, or its effects on health and well-being. Sleepless is also a vivid, economical word for describing someone who remains awake despite exhaustion or in spite of the expectation that they should be sleeping.
adjectiveUnable to fall asleep or remain asleep. It can also describe a period of time that is spent awake rather than resting.
- Not able to fall asleep or remain asleep.
- Of a period of time: marked by continued wakefulness rather than sleep.
"After a sleepless night, she fell asleep for a few minutes in the train."
"He lay sleepless until dawn, listening to the rain."
"The sleepless hours passed slowly as she waited for news of her son."
Sleepless is an elegant act of subtraction: sleep plus the old suffix meaning “without” produces a word for being kept awake.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of sleepless
Sleepless was formed in English from “sleep” and the suffix “-less,” meaning “without” or “lacking.” “Sleep” descends from Old English slǣpan, while the suffix continues Old English lēas, meaning “without”; the combined adjective has been used in English since the early 17th century. Closely parallel formations exist in German as schlaflos and in Dutch as slaaploos, both based on Germanic words for sleep and the corresponding suffix meaning “without.”
Related word forms
How sleepless is actually used
The word is neutral in register and is used in both formal and informal contexts. When describing repeated or prolonged inability to sleep, the noun “sleeplessness” is generally more common.
Easily confused with sleepless
Sleepless means unable to sleep, whereas sleepy means feeling ready or inclined to fall asleep.
Sleepless focuses specifically on the absence of sleep, while restless more broadly describes an inability to remain still or at ease.