虚きょ部ぶきょぶMeanings1nounimaginary partmathematicsMathematics term for the coefficient of the imaginary unit in a complex number. Often contrasted with 実部 (じつぶ, real part).複ふく素そ数すう a+bi の虚きょ部ぶは b です。The imaginary part of the complex number a+bi is b.