What's with this “On reading”/“Kun reading” thing? Is it important to learn both as a beginner?

Question

I was reading this article on Japanese numerals and I first encountered the whole On reading/Kun reading thing, with an additional column on "Preferred reading," which was almost always the On reading.

Do native Japanese know both readings for every Kanji? What influence does this have on the language? What is the use and application of this knowledge? Should I bother learning the non-preferred reading?

Answer 1

Do native Japanese know both readings for every Kanji?

As much has every Roman knew latin. Some kanji have a

• large number of on-readings (consider 行: AN, GYOU, KOU, which are comonly known),
• plus a large number of kun-readings (行: i(ku), okona(u), yu(ku), i(keru), kudari)
• plus several "Nanori" - readings that are used in first names (行: nami, michi,...).

What influence does this have on the language?

Consider the characters 大,人, and 気:

• 大 (KUN:) oo(i), (ON:) DAI, TAI = big
• 人 (KUN:) hito, (ON:) NIN, JIN = person
• 気 (ON:) ki, ke

now combine those:

• 大人 (KUN:) otona = adult
• 人気 (KUN:) hitoke = trace of human life, (also ON: NINKI)
• 大人気 (ON:) DAININKI = very popular

you see, context-sensitive choice of readings.

Should I bother learning the non-preferred reading?

Should you encounter the character in an unfamiliar combination with another character, you'll have to exhaust every possible reading in a Japanese dictionary to either find it, find that the dictionary is insufficient or that you lack another reading, in which case you must consult a separate character dictionary.

Answer 2

Everyone has answered this really well, but I'd like to add some points that I wish someone had told me when I began learning.

The On-yomi is taken from the original Chinese reading of the kanji, and the Kun-yomi is the Japanese reading that has "adopted" the kanji, so to speak. As a general rule, if the kanji is by itself, (as in, it is not attached to other kanji, just hiragana) it generally takes on the Kun-yomi; if the kanji is part of a compound, it (and the other half of the compound) takes on its On-yomi.

Should I bother learning the non-preferred reading?

The answer is "yes". It's the difference between guessing the meaning of a word and being able to read it out loud. That may not sound like much, but it's absolutely essential.

For example: 食べる is pronounced with its Kun-yomi, たべる. 事 on its own is generally pronounced こと, which is the Kun-yomi. If if you combine them 食事, they're both read with their On-yomi: しょくじ

Again, that's very generalized and not always the case, but it's the rule rather than the exception.

Answer 3

With Japanese numbers, yes, you must know both/all readings; it is important to be able to tell 「[九人]{きゅうにん}」 from 「[九時]{くじ}」 from 「[九]{ここの}つ」.

Answer 4

Regarding on'yomi, English has a very similar counterpart. You mentioned numbers, so consider the following:

1. uni-, mono-
2. bi-, di-, duo-
3. tri-, ter-
4. quadri-, tetra-
5. quinque-, penta-
6. sexa-, hexa-
7. septua-, hepta-
8. octo-
9. nona-
10. dec-

Just like in English, the more of these roots (on) that know in Japanese, the easier it will be for you to understand and create new words. Often multiple on readings are generally grouped with other on readings to create a word. In this sense, they are similar to roots.

Do native Japanese know both readings for every Kanji?

Japanese is a citizenship. It can be obtained or lost. There is no correlation between citizenship and linguistic ability. If I am guessing your intent, then you likely mean "native speakers of Japanese".

And to answer the question: a native speaker of Japanese does not know all on and kun readings for every kanji. However, they will know most of all common ones and likely know a few uncommon ones as well.

What influence does this have on the language?

For the most part, loanwords.

What is the use and application of this knowledge?

A wider vocabulary.

Should I bother learning the non-preferred reading?

Absolutely. But why do you say "non-preferred"?