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:
People in Kuwait are avid watchers of the Premier League but non-league is still very much an unknown commodity in the country.
From BBC ● Sep. 29, 2026
Police confirmed the discovery of an unknown woman, in her 20s, on 7 September.
From BBC ● Sep. 28, 2026
Poindexter, a relative unknown, has surged in the meantime.
From Los Angeles Times ● Sep. 25, 2026
Researchers at the University of British Columbia have identified two previously unknown species of sea spider, including one with hairy legs and striking red eyes.
From Science Daily ● Sep. 25, 2026
It’s unknown how many of these papers were printed during this time, but there are at least fifty documented publications.
From "At Last She Stood" by Erin Entrada Kelly
She argued that there were too many "unknowns" about the impacts of concentrations of PCBs on the body and no treatment for those found to have elevated levels in their blood.
From BBC ● Sep. 24, 2026
My husband, 59, and I, 55, are planning to retire over the next few years, and this is one of the biggest unknowns I’m struggling with.
From MarketWatch ● Sep. 18, 2026
“For us to take that risk and gamble with a new factory, tariff unknowns, shipping unknowns—at this point, we are deciding that it’s just not a risk that we’re willing to take,” she said.
From The Wall Street Journal ● Sep. 1, 2026
Phil Dudamel one came with considerable risk and unknowns.
From Los Angeles Times ● Aug. 12, 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.
