unknown
Americanadjective
-
not known; not within the range of one's knowledge, experience, or understanding; strange; unfamiliar.
-
not discovered, explored, identified, or ascertained.
the unknown parts of Antarctica.
-
not widely known; not famous; obscure.
an unknown writer.
noun
-
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.
-
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
-
not known, understood, or recognized
-
not established, identified, or discovered
an unknown island
-
not famous; undistinguished
some unknown artist
-
a person or thing whose action, effect, etc, is unknown or unpredictable
noun
-
an unknown person, quantity, or thing
-
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.
Newport Beach’s Police Assn. blamed social media for a viral “TikTok takeover,” though in that instance, it’s unknown how many posts were made or how the organizing took place.
From Los Angeles Times • Jul. 10, 2026
Schiaparelli's creative director Daniel Roseberry's haute couture collection for Autumn/Winter 2026-2027 was entitled The Call of the Void, which he says was "a total surrender to an unknown creative process".
From BBC • Jul. 9, 2026
As a child, Mr. Coppola stayed close to home, “afraid of the unknown, of being alone, of losing friends and family should I venture out of Gowanus, a fear hard to shake.”
From The Wall Street Journal • Jul. 9, 2026
Fery, a virtually unknown British wild card with a triple-digit ranking, has become the emotional heartbeat of Wimbledon while legitimately diverting some national attention from England’s World Cup quest.
From Los Angeles Times • Jul. 9, 2026
With all the strength he could gather, Duane clawed at the snow wall until he forced his way into the lair, ready to face his unknown fate at the mercy of the dragon monster.
From "The Very, Very Far North" by Dan Bar-el
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.
