I was reading [this][1] 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?


  [1]: http://en.wikipedia.org/wiki/Japanese_numerals#Basic_numbering_in_Japanese