Definite description

In logic, a definite description is a term of the form 'the ...'. It is used to describe something. This is more difficult than it first appears, because:
 The thing or person talked about must exist.
 There must be exactly one such person or thing.

Unfortunately, language allows to construct sentences, where the thing or person talked about is not unique, or it doesn't exist

Definite descriptions are called 'empty', if they violate one of the conditions above:  Bertrand Russell used the sentence "The present king of France is bald.".  When Russel wrote this, in the early 20th century, France was a republic, and had no king.

Other famous  mathematicians who wrote about it include  Gottlob Frege, and Peter Strawson.

 Other websites 
 Stanford Encycopedia of Philosophy: Descriptions

Category:Logic