1
a
: not known
It was a world and life, a way of being, utterly unknown to me.—
Avi
AviAn unknown number of cases go unreported.
For some unknown reason, the computer crashed.
b
: not well-known
an unknown writer/artist
When he left, he had been unknown. Now he was famous.—E. B. White
E. B. White2
: having an unknown value
an unknown quantity
1
a
: one that is not known or not well-known
especially
: a person who is little known (as to the public)
The director cast an unknown in the lead role.
b
the unknown
: a place, situation, or thing that is not known or understood
explorers venturing into the unknown
c
: something that is not known or not yet discovered
There are too many unknowns to go forward with the project.
2
a
: a symbol (such as x, y, or z) in a mathematical equation representing an unknown quantity
b
: a specimen (as of bacteria or mixed chemicals) required to be identified as an exercise in appropriate laboratory techniques
Synonyms of unknown
Examples of unknown in a Sentence
Adjective
a disease of unknown cause
Much remains unknown about his early life.
Her music was previously unknown outside of Asia.
An unknown number of cases go unreported.
The victim's attacker was unknown to her.
For some unknown reason, my computer crashed.
a book of unknown poems
Noun
explorers venturing off into the unknown
A fear of the unknown kept her from changing jobs.
The director cast an unknown in the lead role.
We're facing too many unknowns.
Recent Examples on the Web
Wilson McMakin, Los Angeles Times, 26 Apr. 2026
His status, obviously critical to any Minnesota hopes, was unknown.
—Alex Kirshner, New York Times, 26 Apr. 2026
P.r. Lockhart, Hartford Courant, 24 Apr. 2026
It’s been a spell since Godspell debuted its Toronto production in 1972 with a cast of then-unknowns.
—Matthew Carey, Deadline, 23 Apr. 2026
See All Example Sentences for unknown
Examples are automatically compiled from online sources to
show current usage.
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Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
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Adjective
Separatist fighters on Saturday joined Islamic militants in launching one of the biggest coordinated attacks on the Malian army in the capital and several other cities, which left an unknown number of militants dead and at least 16 people wounded, including civilians, the government said.
—Wilson McMakin, Los Angeles Times, 26 Apr. 2026
His status, obviously critical to any Minnesota hopes, was unknown.
—Alex Kirshner, New York Times, 26 Apr. 2026
Noun
Several critics said the legislation introduces too many unknowns, adding that with the artificial intelligence legislation also under consideration, Connecticut is moving towards regulations that could frighten companies looking to grow in the state.
—P.r. Lockhart, Hartford Courant, 24 Apr. 2026
It’s been a spell since Godspell debuted its Toronto production in 1972 with a cast of then-unknowns.
—Matthew Carey, Deadline, 23 Apr. 2026
See All Example Sentences for unknown
Cite this Entry
“Unknown.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unknown. Accessed 28 Apr. 2026.
Copy CitationKids Definition
unknown
1 of 2 adjective
un·known
ˌən-ˈnōn 
: not known
also
: having an unknown value
an unknown quantity
unknown
2 of 2 noun1
: something that is unknown
2
: a symbol (as x, y, or z) representing a quantity whose value is unknown
an equation with two unknowns
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