noun
imaginary number
Mathematical term for a number whose square is a negative real number. Often introduced alongside complex numbers.
虚数単位 i は、二乗すると -1 になる数です。
The imaginary unit i is a number that becomes -1 when squared.
高校数学で虚数を初めて学ぶ。
Students first learn about imaginary numbers in high school math.
From 虚 (kyo, 'empty' or 'imaginary') + 数 (sū, 'number'), a direct translation of the Western mathematical term 'imaginary number'.