zài / fùshù / píngmiàn / shàng / chúnxūshù / de / shíbù / wéi / líng / xūbù / tōngcháng / shì / fēilíng / shíshù

在复数平面上，纯虚数的实部为零，虚部通常是非零实数。

On the complex plane, a purely imaginary number has a zero real part and usually a nonzero imaginary part.