Sino-Japanese vocabulary
Most Chinese loanwords are nouns, and they are often made up of more than one kanji (Chinese characters used in Japanese). Most kanji have two different kinds of pronunciation, on'yomi (the pronunciation of the kanji borrowed from Chinese) and kun'yomi (the native pronunciation of Japanese words that use the kanji). Yamato kotoba words use the kanji's kun'yomi. While Japanese usually use the kun'yomi for words of just one kanji, like 火 (on'yomi: ka, meaning: fire) which is pronounced hi, and 山 (on'yomi: san, -zan, meaning: mountain) which is pronounced yama, when you put together the two kanji, 火山, the word will not be pronounced by their kun'yomi as hiyama, but rather they will be pronounced by their on'yomi as kazan, which the compound word fire+mountain means "volcano".