On the Origin and Precise Definition of the Term 'Surd' So, in the course of last week's class work, I ran across the Maple function surd() that takes the real part of an nth root. However, conversation with my professor and my own research have failed to produce even an adequate definition of the term, much less a good reason for why it is used in that context in Maple.  Various dictionaries indicate that it refers to certain subsets (perhaps all of?) the irrationals, while the Wikipedia reference link uses it interchangeably with radical.  However, neither of those jive with the Maple interpretation as $\mbox{Surd}(3,x) \neq\sqrt[3]{x}\;\;\;\;\;\;\;x<0$.
So, the question is: what is a good definition for "surd"?
For bonus points, I would be fascinated to see an origin/etymology of the word as used in mathematical context.

An irrational root of rational number is defined as surd. An example is  a root of (-1)
