unknown
Americanadjective
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not known; not within the range of one's knowledge, experience, or understanding; strange; unfamiliar.
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not discovered, explored, identified, or ascertained.
the unknown parts of Antarctica.
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not widely known; not famous; obscure.
an unknown writer.
noun
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a thing, influence, area, factor, or person that is unknown.
the many unknowns in modern medicine; The director cast an unknown in the leading role.
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Mathematics. a symbol representing an unknown quantity: in algebra, analysis, etc., frequently represented by a letter from the last part of the alphabet, as x, y, or z.
adjective
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not known, understood, or recognized
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not established, identified, or discovered
an unknown island
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not famous; undistinguished
some unknown artist
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a person or thing whose action, effect, etc, is unknown or unpredictable
noun
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an unknown person, quantity, or thing
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maths a variable, or the quantity it represents, the value of which is to be discovered by solving an equation; a variable in a conditional equation
3y = 4x + 5 is an equation in two unknowns
Other Word Forms
- unknownness noun
Etymology
Origin of unknown
First recorded in 1250–1300, unknown is from the Middle English word unknow(e)n. See un- 1, known
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
While the war’s duration is unknown, Lee looks at seven major conflicts dating back to 1900 and finds equity markets have a habit of troughing early on because investors “price adverse risks early and quickly.”
From MarketWatch • Apr. 1, 2026
It’s unknown whether Hegseth was able to invest in other defense companies or similar funds.
From Salon • Mar. 31, 2026
A search of the area did not yield more human remains and it was unknown to whom it belonged.
From Los Angeles Times • Mar. 30, 2026
This challenges long-standing assumptions and highlights how much remains unknown about the early evolution of apes and humans.
From Science Daily • Mar. 27, 2026
The more than nineteen thousand recovered objects have provided invaluable insights into topics ranging from previously unknown methods of ancient naval warfare to the earliest history of musical instruments.
From "Shipwrecked!" by Martin W. Sandler
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
