unknown quantity

Definition of Unknown Quantity in English :

1. unknown quantity

a factor in a given situation whose bearing and importance is not apparent

Example Sentences:
'I don't know what the new man will do; he's still an unknown quantity'

2. unknown, unknown quantity

a variable whose values are solutions of an equation

WordNet Lexical Database for English. Princeton University. 2010.

Unknown Quantity

a person or thing whose action, effect, etc, is unknown or unpredictable

noun

1. another name for unknown (sense 6)

a person or thing whose action, effect, etc, is unknown or unpredictable

He's an unknown quantity.

To Margaret the outside world was an unknown quantity.

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