there is no השימוש של האוניומי . it's just another reading of the kanji. as been said before, usually it will take at least 2 kanji so that their onyomi will make a word. the kanji of today is a good example for an onyomi that makes a word by itself. EN=YEN. it is more common for a kunyomi to be a word by itself but still most of the kunyomi will make a word only with the addition of some hiragana. it's very rare for onyomi and kunyomi to mix in the same word.
האוניומי והקוניומי הם צורת הקריאה של הקנג'י, כן? זה בעצם פשוט - איך נקרא את המילה? מבחינת ההגיה שלה? ורק צריך להבדיל בכללים מתי נקרא את האוניומי שלה ומתי הקוניומי?
you but i think you just about got it. only there are no real rules when to use which, you have to know the words. there are guidlines however. for example, adjectives and verbs will almost always be represented by kunyomi as they need hiragana to comlete them.
