The general rule to choose between kun (とし) and on (ネン) readings does not seem to work here. Are 今年, 去年, 来年, 毎年, 半年, etc. different kinds of compounds justifying using different readings? Is this the usual rule applied in a subtle or complicated way?

  • 4
    What general rules did you have in mind? Perhaps you could describe how they appear to break your rules so that answerers can answer your question in a more specific way.
    – Flaw
    Commented Feb 18, 2019 at 11:15
  • 2
    Additionally, a bunch of the ones you mentioned have multiple readings.
    – Leebo
    Commented Feb 18, 2019 at 11:58
  • 3
    exception exist, they will always exist. Commented Feb 18, 2019 at 12:15
  • @Leebo Some readings being more common than others for a given word, there is still a difference between them. Commented Feb 19, 2019 at 7:05

2 Answers 2


I think it might be much more helpful for you to think of "words" having "writings" rather than "characters" having "readings".

For instance, as a speaker or learner or Japanese you know the "word" きょう(today) and you know the "word" あした(tomorrow). Then, you learn how to "write" or "spell" these words:


Then, maybe later you pick up the word あす(also meaning tomorrow) and you ask, how do I write that? And the teacher/your mom/おばあちゃん etc. says "It's written the same way as あした". You think, "Oh, OK"... and you go about your business.

Then, you are taught how to write the word you know for yesterday(昨日{きのう})and you also learn how to write the days of the week like, 日曜日{にちようび}、月曜日{げつようび}、火曜日{かようび}、etc.

At some point you take a class trip to 日光{にっこう} and you have such a great time that you want to write a letter to your おばあちゃん to tell her all about it.

Maybe you write something like this in your letter,


  • Yesterday, (we) went on a field trip to Nikko. It was a lot of fun! (We) came back on Sunday. (We) are coming to your house tomorrow. I want to show you the photos (I took in Nikko).

As you were writing your letter, you didn't think about whether the character「日」is read のう、にっ、にち、び、す、した and neither did your おばあちゃん as she was reading it.

The point of the story is that thinking of characters as having readings is often a bit like putting the cart before the horse. Most of the time, especially in the beginning, you will already be familiar with a word and then you will learn how to write/spell/read it.

Later on, when you come across a word only in writing that you do not know you will likely know how to look it up and learn the pronunciation and meaning together (though you could probably guess from your experience with other words and characters).

Just to reiterate, it is much more helpful to think of words that have writings, rather than characters that have readings. All the more so for very common words.

To directly answer your question, there is no subtle rule in these cases as to how a word will be written, even some on-yomi are usually written in kana. (さっそくがん、そろばんぜんぜん

  1. First you learn a word
  2. Then you learn how it can be written
  3. Then you encounter it in the world and decide how to read it

If there is any general rule to comment on, I think it would just be that on-yomi tend to be more formal or academic, whereas kun-yomi tend to be more frank or poetic. So if you have a choice, like in the case of,

  • 毎年{まいねん}(on-yomi + on-yomi)
  • 毎年{まいとし}(on-yomi + kun-yomi)

...you would probably want to read まいねん if the context is formal, and まいとし if it is not formal.

  • ことし、こんねん → 今年

  • まいとし、まいねん → 毎年


As you say, there are general rules that can help a reader know when a kanji should be read using onyomi and when to use kunyomi, but those rules are general and not universal. It is generally the case that onyomi are used for compounds, but that rule is not universal. As with any language, one of the challenges of mastering Japanese is learning both the generally applicable rules and the exceptions to those rules.

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