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
- 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.
The fate of the weapons operator -- who sits behind the pilot during flight -- remains unknown.
From Barron's • Apr. 3, 2026
Researchers at Oregon Health & Science University have identified a previously unknown system inside cells that acts like internal "trade winds," rapidly carrying important proteins to the front edge of the cell.
From Science Daily • Apr. 1, 2026
The value of these resources remains unknown, but could be massive.
From BBC • Mar. 31, 2026
Now it’s time for a new leap into the unknown.
From The Wall Street Journal • Mar. 30, 2026
I stumbled outside, glad to be free of them both, though my stomach crawled with fear of the unknown.
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.
