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

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 speakers 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

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.