: 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, 29 June 2025
The actual cost of the wedding is unknown, but Venice regional governor Luca Zaia originally estimated the cost between 20 million-30 million euros, or $23 million-$34 million, in a June 24 Reuters article.
—Jay Stahl, USA Today, 29 June 2025
Erik Sherman, Forbes.com, 26 June 2025
There are still many unknowns about the special election to replace Hancock mid-term, including when the election will be held.
—Eleanor Dearman, Fort Worth Star-Telegram, 24 June 2025
See All Example Sentences for unknown
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Adjective
Currently, there is no data indicating the containment progress of the fire and its cause remains unknown.
—Ca Wildfire Bot, Sacbee.com, 29 June 2025
The actual cost of the wedding is unknown, but Venice regional governor Luca Zaia originally estimated the cost between 20 million-30 million euros, or $23 million-$34 million, in a June 24 Reuters article.
—Jay Stahl, USA Today, 29 June 2025
Noun
There are too many unknowns, too much crawling around strange spaces.
—Erik Sherman, Forbes.com, 26 June 2025
There are still many unknowns about the special election to replace Hancock mid-term, including when the election will be held.
—Eleanor Dearman, Fort Worth Star-Telegram, 24 June 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 13 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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