Why does “ruby” mean “furigana”?

  1. What is furigana?
  2. What is “rubi”?
  3. How “ruby” came to Japan and became “rubi”
  4. The meaning of “rubi” today
  • Japanese translation (和訳)


1. What is furigana?

Do you know “furigana”? 

When you read a Japanese text, you sometimes see a small hiragana near a Chinese character. It is placed above the Chinese character in a horizontal text (see below). Those hiragana indicate the pronunciation of the Chinese characters and are called “furigana”.

An image to show an example of “ruby” in the horizontal text

Furigana is a compound word of the “masu” stem of the verb “furimasu” meaning to assign and “kana” meaning hiragana or katakana, and means assigned hiragana or katakana.

Traditional Japanese writing is presented in vertical text. In this case, furigana is placed on the right side of the Chinese characters. 

An image to show an example of “ruby” in the vertical text
Often furigana is typset vertically

2. What is “rubi”?

“Rubi” means furigana, but I didn’t use the word when I was a student. I first noticed when my boss used it while I was working as an editor, and when we communicated with typographers. 

So I thought it was a term used in the publishing business, without knowing why.

After many years, when I learned to type in Word, I found the function to allow me to put furigana for a Chinese character. This function was indicated as “ruby” in English like a jewel. 

Since “rubi” and “ruby” sounded very different to me, I thought they had nothing to do with each other. I was wrong.

3. How the English “ruby” became “rubi” in Japanese

In the 19th Century, British typographers referred to different font sizes by specific names. For example, type with a height of 6.5 point was called “emerald”, 5.5 point “ruby”, 5 point “pearl” and 4.5 point “diamond”. They used these words for interlinear annotations.

Turning to Meiji Japan (1867-1911), Japan received an influx of Western culture. As one example of the Western influence, newspaper publishing and letterpress printing began. Some publishers typeset furigana on Chinese characters so that people without higher education could read their articles and advertisements. 

An image of a 19th century Japanese newspaper with ruby
The photo is a part of the first issue of Asahi Shimbun, Janaury 25, 1879.

The size of a font in newspapers was shown with a number and a unit “goo (号)”. For example, they used 5-goo for the main text and smaller 7-goo for furigana. 

And the 7-goo was very close to the British “ruby” size. So they first referred to the size as “rubi”, but then the meaning changed to indicate typeset furigana of any font size.

By the way, in American English, the size of “ruby” was called “agate”. We don’t know why that word didn’t enter Japanese, but as a retrospect, “rubi” is better than “agatto” since it’s shorter.

4. The meaning of “rubi” today

In today’s Japanese, “rubi” is just another name for furigana. But there is a hint of history in the “professional” atmosphere around it.

[End of the English post]


  1. とは?
  2. 「ルビ」とは?
  3. えいの「ルビー」からほんの「ルビ」へ
  4. 現在げんざいの「ルビ」


1. とは?










何年なんねんもたってワード文書ぶんしょ使つかかたならったとき、かんけられるのうりました。こののうは、宝石ほうせきのように「ルビー Ruby」というえいしめされます。


3. 「ルビー」がどのように「ルビ」となったか







4. 現在げんざいの「ルビ」



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