Japanese also invented many of its own kanji to name things that could be found in Japan, but not China (usually plants and animals). These are called "kokuji" (kanji: 国字, hiragana: こくじ) meaning "national characters", or "wasei-kanji" (kanji: 和製漢字, hiragana: わせいかんじ) meaning "Japanese-made Chinese characters". "Kokuji" include the names of fish like "iwashi" (kanji: 鰯, hiragana: いわし, meaning: sardine), "tara" (kanji: 鱈, hiragana: たら, meaning: codfish), and "kisu" (kanji: 鱚, hiragana: きす, meaning: sillago), and trees like "kashi" (kanji: 樫, hiragana: かし, meaning: evergreen oak), "sugi" (kanji: 椙, hiragana: すぎ, meaning: Japanese cedar), and "kaba" or "momiji" (kanji: 椛, hiragana: かば/もみじ, meaning: birch/maple). Most "kokuji" only have kun'yomi because they are "yamato kotoba", but some kanji also have on'yomi, like 働 (on'yomi: dō どう, kun'yomi: hatara(ku) はたら(く), meaning: work), and some have only on'yomi, like 腺 (on'yomi: sen せん, meaning: gland). 