: not known or not well-known
also
: having an unknown value
an unknown quantity
1
: one that is not known or not well-known
especially
: a person who is little known (as to the public)
2
: something that requires discovery, identification, or clarification: such as
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
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
Ca Wildfire Bot, Sacbee.com, 11 July 2025
The early childhood development nonprofit was notified that incoming grants would be awarded this summer, but the exact date was unknown, CEO and President Kara Waddell said in a statement in May.
—Fort Worth Star-Telegram, 11 July 2025
Paul A. Thompson, Pitchfork, 11 July 2025
My father handled most of the issues, but now suffers from dementia, so there are a lot of unknowns.
—R. Eric Thomas, Chicago Tribune, 10 July 2025
See All Example Sentences for unknown
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Adjective
At this time, details about the containment or cause of the fire are unknown.
—Ca Wildfire Bot, Sacbee.com, 11 July 2025
The early childhood development nonprofit was notified that incoming grants would be awarded this summer, but the exact date was unknown, CEO and President Kara Waddell said in a statement in May.
—Fort Worth Star-Telegram, 11 July 2025
Noun
Unlike with Batman, which has lured major stars, the directors and producers of Superman movies have generally cast young, strapping unknowns, a certain blankness as the baseline for both Kal-El and Clark Kent.
—Paul A. Thompson, Pitchfork, 11 July 2025
My father handled most of the issues, but now suffers from dementia, so there are a lot of unknowns.
—R. Eric Thomas, Chicago Tribune, 10 July 2025
See All Example Sentences for unknown
Cite this Entry
“Unknown.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unknown. Accessed 18 Jul. 2025.
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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