Postby QuackingShoe » September 28th, 2008 6:15 am
You can guess by how it's used (as described on the website), and simply how it sounds (you rapidly learn to tell the difference between Chinese-derived and Japanese-derived sounds; they're just different), but also any dictionary that lists the readings of a kanji writes the onyomi in katakana and the kunyomi in hiragana. Or in those (blurgh) romaji ones, I believe onyomi are ALL CAPS, but I might have it the other way around, it's been a long time since I've seen one.