[FOM] origin of "real"

Alasdair Urquhart urquhart at cs.toronto.edu
Tue Sep 20 10:28:32 EDT 2011

The origin of the term lies in the 17th century,
I think, in connection with the solution of
algebraic equations.  For example, here is
Descartes in "La Geometrie" (1637):

 	Neither the true nor the false roots are
 	always real, sometimes they are imaginary;
 	that is, while we can always imagine as
 	many roots for each equation as I have
 	assigned, yet there is not always a definite
 	quantity corresponding to each root we
 	have imagined.

Thus, the term "real" was introduced as a contrast
to "imaginary."  This does have some connection
with the explanation offered below, since
Descartes no doubt thought of "real solutions"
as being solutions in the "real world."

On Mon, 19 Sep 2011, Thomas Lord wrote:

> I have a history and semantics question that this
> group might easily be able to answer (but elsewhere
> is hard to find an answer for):
> Who coined the term "real" as in "real number"
> and *why* did they pick that word?
> I ask because in a discourse on the programming
> language theory website "Lambda the Ultimate"
> someone wrote:
> "The reason real numbers have the name 'real' is
> because they correspond to measures of the real
> world."
> Retrospectively that sounds plausible but is it
> in fact the origin of the term?

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