Imaginary

a. [Lat. imaginarius, Fr. imaginaire, Sp. imaginario, It. immaginario.] Existing only in imagination or fancy; not real.

*Wilt thou add to all the griefs I suffer Imaginary ills and fancied tortures?* Addison.

Imaginary quantity or expression (Math.), an algebraic expression or symbol having no assignable arithmetical or numerical meaning or interpretation; the even root of a negative quantity; as, √−9, √−a².

Synonyms—Ideal; fanciful; chimerical; visionary; fancied; unreal.

n. (Alg.) An imaginary expression or quantity.