: 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
Joseph V Micallef, Forbes.com, 16 Aug. 2025
Carter's availability is currently unknown, but the defensive star certainly has all eyes on him moving forward.
—Justin Grasso, MSNBC Newsweek, 16 Aug. 2025
Keith M. Phaneuf, Hartford Courant, 31 July 2025
State Judge Steven Hippler last week lifted a gag order but declined the media’s motion to intervene and unseal documents, which could well shed light on the lingering unknowns.
—Elise Hammond, CNN Money, 24 July 2025
See All Example Sentences for unknown
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Adjective
The mash bill is unknown but is believed to be 60%-75% corn, 20%-25% rye, with the balance of malted barley.
—Joseph V Micallef, Forbes.com, 16 Aug. 2025
Carter's availability is currently unknown, but the defensive star certainly has all eyes on him moving forward.
—Justin Grasso, MSNBC Newsweek, 16 Aug. 2025
Noun
But an administration spokesman offered perspective Tuesday and said analysts made their best projections amid many unknowns.
—Keith M. Phaneuf, Hartford Courant, 31 July 2025
State Judge Steven Hippler last week lifted a gag order but declined the media’s motion to intervene and unseal documents, which could well shed light on the lingering unknowns.
—Elise Hammond, CNN Money, 24 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 19 Aug. 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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