Kanji by itself, kanji with okurigana (letters which are sent out from the kanji) and jukugo (compound words) with okurigana use KUNyomi.
ONyomi is only used with jukugo.
Nouns: no-okurigana words.
Verbs: okurigana words.
almost always.
Radicals!
Some (26?) radicals Im learning from wanikani (Profile: https://www.wanikani.com/community/people/RastrilloG), realy exciting. The radicals are the “things” (sorry) that you use for the kanjis. For example, the kanji 内 (house) has the radicals for “person” and “box”.
Japanese’s Alphabets | Hiragana, Katakana and Kanji
The three Japanese “alphabet” are:
Hiragana: is used in difficult kanji, words with no kanji, particles and suffixes.
Katakana: is used in foreign words, scientific words, onomatopoeia, emphasis, food.
Kanji: is used in most vocabulary.
Japanese Learning Log 