Rules and tools for assigning furigana


It often happens that I want to supply the furigana (振{ふり}仮{が}名{な}) for some
kanji-containing word, but can't figure out the right assignment of the kana
to the kanji.

* * *

To be clear, the problem here is **not** that of finding the (overall) reading
of a word. I have several ways to deal with this.

The problem I'm referring to here is that of assigning _fragments_ of the
overall reading _to each separate kanji_ in a kanji combination.

For example, the 2-kanji word 昨日 (=yesterday) can be read either as さくじつ or as
きのう. For the first reading, the assignment of kana to kanji follows readily
from the fact that さく and じつ are standard readings of 昨 and 日, respectively.
For the second reading, however, the same reasoning won't work.

Another example is the word 微笑む (=to smile) whose reading is ほほえむ. On the one
hand えむ is a standard reading for 笑む, but ほほ is not a standard reading for 微.
The simplest resolution here is to assume that ほほ is a non-standard reading of
微, and leave it at that. BUT, there is also the formal (if admittedly
strained) possibility that here we have a case of _two_ non-standard readings,
namely ほ for 微 and ほえむ for 笑む. If I had to guess, of course, I would go for
the first (ほほ|えむ) split, but the reason I am posting this question is that _I
don't want to guess_.

Also, in all cases, the assignment problem could be bypassed entirely, by
assigning the furigana to the kanji combination _as a whole_ , without
assigning the various parts of the furigana string to individual kanji.
Following this convention, one would say, for example, that きのう is the
furigana for the kanji _combination_ 昨日, _as a whole_ , and that ほほえ is the
furigana for the kanji combination 微笑 (in 微笑む), _as a whole_ 1. The latter, in
particular, strikes me as unlikely, somehow, but when it comes to the Japanese
writing system, I've learned to disregard my commonsense.

* * *

One possible source of help with such questions would be a set of
authoritative rules for doing such furigana assignments and/or authoritative
sources that publish such assignments (which may be necessary if the rules
suffer from many exceptions).

Alternatively, there could be apps and online tools that provide the correct
assignment.

I'm interested in candidates in all these areas.

* * *

1Granted, I have run into situations where, due to the relative font sizes and
character spacing of the main text and the furigana, there was _little or no
visual difference_ between a per-character assignment and a per-combination
assignment. For example, for the reading はたち of the word 二十歳 (=20-years old),
it may be that one gets pretty much the same result, _visually_ , whether one
assigns furigina to the individual kanji (二 は; 十 た; 歳 ち), or to the
combination as a whole (二十歳 はたち). Still, such cases of apparent equivalence
are rare and too dependent on the vagaries of typography to rely on.




It is more a matter of typography than of orthography.

  * [ふりがなを入れる時の5つの決まり事](https://blog.printbiz.jp/archives/1008686834.html)

>
> 漢字1文字ごとに読み仮名を振るルビをモノルビ、単語単位に振るルビをグループルビといいます。文字と読みの関係を学ぶ目的の文章、教科書や教材（特に低年齢用）ではモノルビが使用されます。漢字の読み方を学ぶ場合ですね。
> 熟字訓や当て字についてはグループルビが使用されます。特別な読み方の地名にも、グループルビが用いられます。

Roughly:

> Assigning reading per character is called _Mono-ruby_ and per word is called
> _Group-ruby_. Mono-ruby is used for textbooks which is intended for learning
> relationships between characters and reading. Group-ruby is used for jukuji-
> kun and [ateji](https://ja.wikipedia.org/wiki/%E5%BD%93%E3%81%A6%E5%AD%97)
> or place names with special readings.

Note that normally readable kanjis are not furigana-ed in most cases ([Rules
for **when** to put
furigana](https://crd.ndl.go.jp/reference/modules/d3ndlcrdentry/index.php?page=ref_view&id=1000116191)).
Also sometimes mono-ruby takes more space (誕{たん}生{じょう}日{び} vs 誕生日{たんじょうび} from
[here](https://www.tairapromote.co.jp/column/288/)), so may be less preferred.

At best, what you could do is to find a list of jukuji-kun/ateji and use
group-ruby for them/mono-ruby otherwise.




It is more a matter of typography than of orthography.

  * [ふりがなを入れる時の5つの決まり事](https://blog.printbiz.jp/archives/1008686834.html)

>
> 漢字1文字ごとに読み仮名を振るルビをモノルビ、単語単位に振るルビをグループルビといいます。文字と読みの関係を学ぶ目的の文章、教科書や教材（特に低年齢用）ではモノルビが使用されます。漢字の読み方を学ぶ場合ですね。
> 熟字訓や当て字についてはグループルビが使用されます。特別な読み方の地名にも、グループルビが用いられます。

Roughly:

> Assigning reading per character is called _Mono-ruby_ and per word is called
> _Group-ruby_. Mono-ruby is used for textbooks which is intended for learning
> relationships between characters and reading. Group-ruby is used for jukuji-
> kun and [ateji](https://ja.wikipedia.org/wiki/%E5%BD%93%E3%81%A6%E5%AD%97)
> or place names with special readings.

Note that normally readable kanjis are not furigana-ed in most cases ([Rules
for **when** to put
furigana](https://crd.ndl.go.jp/reference/modules/d3ndlcrdentry/index.php?page=ref_view&id=1000116191)).
Also sometimes mono-ruby takes more space (誕{たん}生{じょう}日{び} vs 誕生日{たんじょうび} from
[here](https://www.tairapromote.co.jp/column/288/)), so may be less preferred.

At best, what you could do is to find a list of jukuji-kun/ateji and use
group-ruby for them/mono-ruby otherwise.

