an unknown and unexplored region
"they came like angels out the unknown"
a variable whose values are solutions of an equation
"The algorithm struggled to converge because it treated the unknown as a fixed constant rather than a variable whose values were solutions of an equation."
A variable (usually x, y or z) whose value is to be found.
"When solving for the missing angle in the triangle, we can label that unknown as theta."
In plain English: An unknown is something that you do not know about or have never seen before.
"The unknown remains a constant mystery in human history."
past participle of unknow
"I remained unaware of his identity until he revealed himself at the meeting."
In plain English: To unknown something means to not know it at all.
"The detective did not know the suspect's real name."
being or having an unknown or unnamed source
"a poem by an unknown author"
"corporations responsible to nameless owners"
"an unnamed donor"
Not known; unidentified; not well known.
"The package was returned to sender because the return address listed an unknown recipient who had never been seen by anyone in the neighborhood."
In plain English: Something unknown is when you don't know what it is or where it came from.
"We tried to call our unknown number, but it went straight to voicemail."
Usage: Use this adjective to describe something whose identity or nature has not been determined, such as an unknown caller or variable in mathematics. It differs from synonyms like unfamiliar by emphasizing a complete lack of identification rather than simply being new or strange.
The word unknown comes from Middle English and is formed by adding the prefix "un-" to the past participle of "know." It has retained its original meaning throughout history, referring simply to something that is not recognized or familiar.