The Collaborative International Dictionary
Imaginary \Im*ag"i*na*ry\, a. [L. imaginarius: cf. F. imaginaire.] Existing only in imagination or fancy; not real; fancied; visionary; ideal.
Wilt thou add to all the griefs I suffer
Imaginary ills and fancied tortures?
--Addison.
Imaginary calculus See under Calculus.
Imaginary expression or Imaginary quantity (Alg.), an algebraic expression which involves the impossible operation of taking the square root of a negative quantity; as, [root]-9, a + b [root]-1.
Imaginary points, lines, surfaces, etc. (Geom.), points, lines, surfaces, etc., imagined to exist, although by reason of certain changes of a figure they have in fact ceased to have a real existence.
Syn: Ideal; fanciful; chimerical; visionary; fancied; unreal; illusive.
Usage examples of "imaginary quantity".
What I would like to know now, Professor, said the reporter, is just what this imaginary quantity is all about.
We've got a predicted reaction which includes an imaginary quantity!