Composite number is translated as 合数, which do make sense; Prime number is called 素数, what does 素 means here?

Is it possible to trace the source of such translation?

  • OP cross-posted this same question to Japanese SE. Anyways, your question appears answered on p. 241 of Christopher Seeley's Complete Guide to Japanese Kanji, 2006 2nd ed. >![](i.imgur.com/yag9fiF.jpg)
    – user35024
    Nov 26, 2022 at 9:59

4 Answers 4


「素」generically means basal, essential, intrinsic, primal. Hence you have vocabulary like

  • 元素 (atom), the fundamental constituent of matter (well, the name was given before they discovered subatomic particles)
  • 詞素 (morpheme), the fundamental constituent of words
  • 要素 (essential factor)
  • It 's very interesting to find that google translate `primer number' to '素数' in Japanese. So it borrowed from Japanese. Do you know some Japanese about the word 素?
    – Wizard
    Dec 9, 2019 at 14:01
  • atom is reasonable, prime number can not be decomposed any more.
    – Wizard
    Dec 9, 2019 at 14:03
  • 1
    @Algebra well「素」in Japanese shares the base, primal meanings with Chinese. As for whether 素數 originated in Japanese, I'm not sure. They might have coined it - there's a heap of words in Chinese that originated from Wasei-Kango.
    – dROOOze
    Dec 9, 2019 at 14:10

素 can mean prime in some way. See this definition in dictionaries:




素 can mean 物的基本成分 (basic element of something) as an extension from its base meaning of plain, natural, pure, unmodified.

In its synonym 质数, 质 also means the nature of something or being plain and simple.


素数 is a Japanese mathematic term for "prime number", which equates to the Chinese term "质数" - the natural numbers greater than 1, that have only two factors, one and the number itself.

Note that "质" has the meaning of "单纯", which is also reflected by 素 - a pure, unmodified element, such as "朴素", "元素".

素数(そすう、英: primeあるいはprime number)

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