unknown

Not known or understood by anyone.

• The cause is unknown.
• Her exact date of birth remains unknown.
• They found a substance of unknown origin.

Similar words: undetermined, unexplained

Opposites: known

Common phrases: unknown cause, remain unknown, unknown origin

Not recognized, named, or familiar to many people.

• An unknown caller left a message.
• The painting was by an unknown artist.
• She was relatively unknown before her first film.

How to use it: unknown to someone (The young writer was unknown to most readers.)

Similar words: unidentified, unfamiliar, obscure

Opposites: famous, well-known

Common phrases: unknown artist, unknown caller, relatively unknown

A number represented by a letter in a maths problem whose value you must find.

• Find the unknown in this equation.
• The letter x represents an unknown.
• We solved two equations with two unknowns.

Similar words: unknown variable

Common phrases: solve an unknown, one unknown, two unknowns