Composite number is translated as 合成数 (by google translation to Japanese), which makes sense.

Prime number is called 素数, but what does 素 means here?

I am trying to trace the source of it. We borrowed the translation of it decades ago, so it does not very conceivable to illustrate it by the Chinese dictionary items.

I would appreciate it very much if answered in English.

  • 1
    What definition did you find? And why do you think it doesn't fit?
    – Leebo
    Dec 9, 2019 at 14:29
  • since 素 means base, essential in Chinese which really make sense of the prime(primitive), Nonetheless, many borrowed translations from Wasei-kango are ridiculous. I am curious about it's origin which reasonable by accident.
    – Wizard
    Dec 9, 2019 at 14:39

1 Answer 1


From an etymological standpoint, the character 素 itself originates from China. In about the 5th century AD, Japan started using Chinese characters. Before this point, there was no Japanese writing system, and modern hiragana and katakana are derived from the Kanji that was first introduced to Japan around this time period.

From what I understand the Japanese language obtained most of their Kanji from China between the 5th and 9th centuries.

Over the centuries, there were many Japanese scholars that went to either Korea or China to study, and they returned with additional Kanji characters that they then introduced to the Japanese language. Due to the lack of detailed records about what character came when, I cannot be more specific than this: The character started being used in the Japanese language sometime during or even after the 5th century AD.

The thing is, the scholars that went to China had their disagreements about the meaning and pronunciation of the Chinese characters. These disagreements can be derived from one of a number of factors including the region the scholar studied, or when the scholar studied (things change with time). This is why we sometimes see multiple Chinese readings for characters. A classic example is , which has the Chinese readings ジン, and ニン. This discrepancy likely stems from the fact that two different scholars disagreed on how the character was truly pronounced (or they were confused), and so they taught what they understood. As the language developed both readings became accepted.

Just as Kanji can have multiple ON-readings, the same issues sprouted up about what the characters actually meant. Remember, that Chinese was not the Japanese scholar's first language, so at times the meaning of words and characters were occasionally garbled by the translation attempts of the scholars. In addition, as characters were re-introduced into the Japanese language, the pronunciation of the Chinese reading also occasionally evolved. Though I do not speak Chinese personally, I have seen cases where characters will take a different meaning in Japan.

So to answer more directly, the character 素 likely was introduced to Japan between the 5th and 9th century AD. Due to the complexities of learning foreign languages, the meaning and ON-readings of the character were probably the source of some discrepancies between early scholars, so the Japanese language evolved to accept the opinions of all the scholars involved.


I realized that I did not answer what 素 means in this context. According to the online dictionaries that I use, 素 can mean: elementary, principle, naked, or uncovered.

In the context of prime numbers, I would take this to mean elementary or principle, as prime numbers cannot be divided into whole numbers.

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    Without consideration, Chinese borrowed the almost all the translations of vocabularies referring Science in 1900 from Japanese Wasei-kango which occupy over 80% of academic frequent usage words.
    – Wizard
    Dec 9, 2019 at 15:03
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    @Algebra I failed to mention that the Japanese also created their own Kanji Characters, and 'derived' an ON-reading to fit with those characters. It is not unreasonable for the Chinese to borrow these terms since the characters would integrate nicely. Additionally, the fact that Japan was more technologically advanced at the time just made the borrowing of those characters more inevitable than anything.
    – ajsmart
    Dec 9, 2019 at 15:05
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    You wrote: "The thing is, the scholars that went to China had their disagreements about the meaning and pronunciation of the Chinese characters. This is why we sometimes see multiple Chinese readings for characters." Different readings are thought to have been borrowed from different places in China at different times. Rather than being a disagreement among scholars about the true pronunciation in Middle Chinese, it makes more sense to say that more than one pronunciation was borrowed because more than one pronunciation was actually used.
    – user1478
    Dec 9, 2019 at 16:11
  • I attempted to take that into account in my original post, but I guess it needed some touching up. Let me know if my edit does/doesn't satisfactorily address your comment.
    – ajsmart
    Dec 9, 2019 at 18:52

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