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1 英语原意

虚数：Imaginary number

2 英文解释

2.1 What is a Imaginary number?

The number whose square results in negative results is called an Imaginary number.

虚数，平方等于-1，即 i²=-1。

Imaginary numbers are numbers that can be written as a multiple of the imaginary unit i, where i is defined as the square root of -1. Examples include 2i, −3i, and 5i.

In simple words, the square root of negative numbers is called an imaginary number. They are called imaginary numbers as we cannot associate them with any real-life examples.

They are represented by “i” and are pronounced as iota at its value is,

i = √-1

2.2 History and Naming

The concept of imaginary numbers was first introduced in the 16th century by Italian mathematician Rafael Bombelli. Initially, the notion was met with skepticism and confusion. They got their name because they were deemed “impossible” and “imaginary,” as they couldn’t be represented on the number line of real numbers.

虚数的概念最早是由意大利数学家拉斐尔·邦贝利（Rafael Bombelli）在16世纪提出的。最初，这个概念遭到了怀疑和困惑。他们之所以得名，是因为它们被认为是“不可能的”和“虚构的”，因为它们不能在实数的数字线上表示。

Imaginary Numbers were once thought to be impossible, and so they were called "Imaginary" (to make fun of them).

虚数曾经被认为是不可能的，因此它们被称为“虚数”（取笑它们）。

But then people researched them more and discovered they were actually useful and important because they filled a gap in mathematics ... but the "imaginary" name has stuck.

但后来人们更多地研究了它们，发现它们实际上是有用和重要的，因为它们填补了数学的空白......但“虚构”的名字一直存在。

And that is also how the name "Real Numbers" came about (real is not imaginary).

这也是“实数”这个名字的由来（实数不是虚构的）。

2.3 Imaginary Numbers are Useful

Complex Numbers, Imaginary numbers become most useful when combined with real numbers to make complex numbers like 3+5i or 6−4i

3 中文解释

虚数是那些平方后得到负数的数。因此，这些是相当于负数的平方根的值。例如，虚数单位（数字 i）等于 -1 的平方根。

参考文献：https://www.mathsisfun.com/numbers/imaginary-numbers.html