unknown

UK: /ˌʌnˈnəʊn/ US: /ʌnˈnoʊn/ ,(un nōn′)

WordReference Random House Learner's Dictionary of American English © 2025

un•known /ʌnˈnoʊn/   adj. 

1. not known;
   not within the range of knowledge, experience, or understanding;
   strange;
   unfamiliar.
2. not discovered, explored, identified, or figured out:
   an unknown amount.
3. not widely known;
   not famous;
   obscure:
   an unknown author.

n. [countable]

4. a person or thing that is unknown.
5. Mathematics a symbol representing an unknown quantity:
   In algebra an unknown is frequently represented by a letter from the last part of the alphabet, as x, y, or z.

WordReference Random House Unabridged Dictionary of American English © 2025

un•known  (un nōn′), adj. 

1. not known;
   not within the range of one's knowledge, experience, or understanding;
   strange;
   unfamiliar.
2. not discovered, explored, identified, or ascertained:
   the unknown parts of Antarctica.
3. not widely known;
   not famous;
   obscure:
   an unknown writer.

n. 

4. a thing, influence, area, factor, or person that is unknown:
   the many unknowns in modern medicine; The director cast an unknown in the leading role.
5. Mathematics a symbol representing an unknown quantity: in algebra, analysis, etc., frequently represented by a letter from the last part of the alphabet, as x, y, or z.

• Middle English unknow(e)noun, nominal See un-¹, known 1250–1300

Collins Concise English Dictionary © HarperCollins Publishers::

unknown / ʌnˈnəʊn/ adjective

1. not known, understood, or recognized
2. not established, identified, or discovered: an unknown island
3. not famous; undistinguished: some unknown artist
4. unknown quantity ⇒ a person or thing whose action, effect, etc, is unknown or unpredictable

noun

1. an unknown person, quantity, or thing
2. a variable, or the quantity it represents, the value of which is to be discovered by solving an equation; a variable in a conditional equation

unˈknownness noun