实数是什么？又被翻译带歪了，直到看到英文 Real number 才恍然大悟

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实数里的“实”是什么意思，谁能想到是“真实”的意思？实数 Real number，就是真实存在的数字，实数是在虚数这个概念出现之后才有的，实数是相对虚数来说的。

1 英语原意

实数：Real number

2 英文解释

2.1 What is a Real number?

A real number is any number that can be placed on a number line or expressed as in infinite decimal expansion. In other words, a real number is any rational or irrational number, including positive and negative whole numbers, integers, decimals, fractions, and numbers such as pi (π) and Euler’s number (e).

实数是可以放在数字线上或以无限十进制展开表示的任何数字。换句话说，实数是任何有理数或无理数，包括正负整数、整数、小数、分数和数字，例如 pi （π） 和欧拉数 （e）。

In contrast, an imaginary number or complex number is not a real number. These numbers contain the number i, where i² = -1.

相反，虚数或复数不是实数。这些数字包含数字 i，其中 i² = -1。

Real numbers are represented by the capital letter “R” or double struck typeface . The real numbers are an infinite set of numbers.

2.2 Why are they called “Real” Numbers?

Because they are not Imaginary Numbers.

因为它们不是虚数。

The Real Numbers had no name before Imaginary Numbers were thought of. They got called “Real” because they were not Imaginary. That is the actual answer!

在虚数出现之前，实数是没有名字的。它们被称为“真实”，因为它们不是虚构的。这才是真正的答案！

3 中文解释

实数，是有理数和无理数的总称。

要想深刻理解这些专业术语，一定要看英语原意啊，明明通俗易懂的英语词语，翻译成中文之后就变得晦涩难懂。