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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unknowns
plural
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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
Derived Forms
Inflected Forms
Nouns
Etymology
Origin of unknown
First recorded in 1250–1300, unknown is from the Middle English word unknow(e)n. See un- 1, known
Explanation
If something is unknown, it's not familiar understood, like the unknown path through the woods you've never explored or your brother's unknown reasons for staying late after school. When you're aware ofor familiar with something, you can describe it as known. Add the prefix un-, or "not," and you get unknown. You'll often find this adjective in the phrase "unknown territory," as in "I totally understand algebra, but calculus is unknown territory." And as a noun, the unknown sometimes represents a whole category of mysterious things: "Our fear of the unknown keeps us from traveling to new places."
Vocabulary lists containing unknown
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.
See Examples For:
A cause of death is unknown, but Haskins had quietly battled Parkinson’s and was candid about other health issues.
From Los Angeles Times ● Sep. 29, 2026
In just two years Johan Manzambi has gone from being an unknown teenager to a European star.
From BBC ● Sep. 29, 2026
Police confirmed the discovery of an unknown woman, in her 20s, on 7 September.
From BBC ● Sep. 28, 2026
It was a love triangle that would change music history: the great and tortured Robert Schumann; his virtuoso wife, Clara; and a young, unknown Johannes Brahms.
From The Wall Street Journal ● Sep. 25, 2026
And then Roz realized that this type of sea slug was unknown.
From "The Wild Robot Protects" by Peter Brown
Recent warnings about the potential dangers of AI show that there are significant unknowns with such a rapid growth of a new industry.
From BBC ● Sep. 15, 2026
But there are also the other known unknowns with any season opener.
From Los Angeles Times ● Sep. 6, 2026
She even suggests assembling a “question collection” in the workplace, to which employees would contribute unknowns for their co-workers to mull over.
From The Wall Street Journal ● Aug. 4, 2026
And what was left, once memories of the crisis faded, were the harms of the choices we made to cope with a whole host of unknowns: the learning losses, socialization issues, and shuttered businesses.
From Slate ● Aug. 3, 2026
But the paper stares back up at me, blindingly blank like the terrifying unknowns of my new fate.
From "Flying Through Water" by Mamle Wolo
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.
