The Japanese language contains many types of words. In colloquial terms, they might be loosely classified according to their respective writing systems: ひらがな語 (hiragana words), カタカナ語 (katakana words), and 漢字語 (kanji words). Written Japanese especially is made up of over 65% kanji words and contains a lot of compound kanji words in particular. The correct term for these kanji compound words is 熟語 jukugo, and they deserve special attention due to the significant contribution they can make to one’s Japanese vocabulary.
Jukugo 熟語 are Japanese words, written solely in kanji, formed by combinations of two or more characters. They are called kanji compounds in English. For example, the word jukugo 熟語 is itself a jukugo. In many cases, the meaning of a jukugo can be deduced from the meaning of its component kanji.
A jukugo is a type of 合成語 (gouseigo) which means compound word [1]. Gouseigo can take several different forms and be written in a mixture of kanji, hiragana and katakana. But the unique thing about jukugo is that they are written in kanji alone. For this reason, jukugo are also referred to as 熟字 (jukuji) or 漢語 (kango). Since kanji can have several different readings for a given character, the correct reading of a jukugo can be tricky.
One study found that words of Chinese origin accounted for 50 to 65% of the total word count written Japanese [2]. Consequently, the most common reading for the kanji of jukugo is the onyomi reading. However, kunyomi readings and mixed onyomi-kunyomi readings also exist. Overall, a high volume jukugo exist in the Japanese language and learning jukugo will really help increase your vocabulary.
In many cases, the meaning of a jukugo as a whole is the combined meaning of its underlying kanji. Take the word 左右 (sayuu) for example, the first character, 左, is left and the second, 右, is right. As a whole, the word means “left and right”. Also note that this word is read さゆう, which is the onyomi reading, rather than ひだりみぎ, which would be kunyomi.
Knowing the meaning of individual kanji is helpful in deducing the meaning of an unknown jukugo, but it is important to know that there are cases in which the meaning of a jukugo is only vaguely or partially related to its component kanji, which can lead to an incorrect deduction of its meaning. This is known as the semi-transparency of kanji [2].
For example, the word 左右, which we just looked at above, has another meaning, which is “influence” or “affect”, as in, to have an influence on something. For example, “your future job prospects are greatly influenced by your education”, 「将来の仕事の展望は学歴に大きく左右されます」. Without a lot of historical knowledge of kanji and how this word developed, it’s hard to know how the combination of “left and right” can end up meaning “influence”.
Interestingly, we get a reprieve on more challenging technical terms [2]. For example, hypotension, which in simpler terms means low blood pressure. In Japanese, hypotension is 低血圧症, read in onyomi as ていけつあつしょう (teiketsuatsushou). The individual kanji have the following meanings, 低: low, 血: blood, 圧: pressure, 症: illness, which make the meaning of the word very transparent.
Overall, knowing the meanings and readings of individual kanji will help you out in many cases (despite some exceptions) when it comes to jukugo, for that reason studying kanji is an important base element of your Japanese vocabulary development. For more detailed information about the importance of learning kanji, I have written about it here.
Two-Kanji Jukugo 二字熟語: The backbone of Japanese Vocabulary
Let’s look at how some common types of jukugo are formed. Below we will look at five types of two-kanji jukugo 二字熟語 (nijijukugo). Two-kanji are the most common type of jukugo, in fact they account for approximately 36% of the 220,000 words listed in Kojien (Shinmura Izuru Kinen Zaidan, 1995), which contains all types of words, kanji words, kana words (hiragana and katakana), and kanji-kana mixed words [3].
Types of Two-Kanji Jukugo 二字熟語
- Front kanji is the subject and rear kanji is the predicate
- Rear kanji is the object or complement of the front kanji
- Front kanji is a modifier or qualifier of the rear kanji
- Kanji with opposite meanings
- Kanji with similar meanings
Two-Kanji Jukugo: Front Kanji Subject + Rear Kanji Predicate
With this type of jukugo, if the two kanji were split apart and formed into a sentence, it would follow the pattern [subject が predicate].
Example words: 私有 Reading: しゆう, shiyuu Meaning: private ownership Deconstruction: 個人や法人が（何かを）所有する。 A private individual or legal entity owns (something). 市営 Reading: しえい, shiei Meaning: city run Deconstruction: 市が（何かを）経営する。 The city operates (something). 人工 Reading: じんこう, jinkou Meaning: human made Deconstruction: 人間が（何かを）工作する。 Humans make (something).
Two-Kanji Jukugo: Rear Kanji Object or Complement of Front Kanji
With this type of jukugo, if the two kanji were split apart and formed into a sentence, it would follow the pattern [noun を verb].
Example words: 洗顔 Reading: せんがん, sengan Meaning: face washing Deconstruction: 顔を洗う。 To wash (one’s) face. 読書 Reading: どくしょ, dokusho Meaning: reading books Deconstruction: 図書（本）を読む。 To read books. 乗車 Reading: じょうしゃ, jousha Meaning: boarding a train, bus etc. Deconstruction: 電車などを乗る。 To board a train (or another type of vehicle).
Two-Kanji Jukugo: Front Kanji Modifies or Qualifies Rear Kanji
With this type of jukugo, if the two kanji were split apart and formed into a sentence, it would follow the pattern [qualifier/modifier (such as an adjective) + noun] or [noun の noun].
Example words: 高級 Reading: こうきゅう, koukyuu Meaning: high rank Deconstruction: 高い階級。A high rank. 植木 Reading: うえき, ueki Meaning: potted plant Deconstruction: 植えた木。A potted plant. 電車 Reading: でんしゃ, densha Meaning: Electric train Deconstruction: 電気の電車。An electric train.
Two-Kanji Jukugo: Kanji with Opposite Meanings
With this type of jukugo, if the two kanji were split apart and formed into a sentence, it would follow the pattern [word at one end of a spectrum and corresponding word at the other end of the spectrum].
Example words: 左右 Reading: さゆう, sayuu Meaning: left and right 南北 Reading: なんぼく, nanboku Meaning: south and north 善悪 Reading: ぜんあく, zenaku Meaning: right and wrong, good and evil
Two-Kanji Jukugo: Kanji with Similar Meanings
With this type of jukugo, if the two kanji were split apart, we would see that they have similar meanings. Back in their combined form, they make word with yet another similar (possibly more precise) meaning.
Example words: 閲覧 Reading: えつらん, etsuran Meaning: Reading while researching the content of written material such as books, newspapers, websites… 閲 – review, inspection 覧 – perusal, see 道路 Reading: どうろ, douro Meaning: road 道 – road, street, way 路 – path, route, road 暗黒 Reading: あんこく, ankoku Meaning: darkness 暗 – darkness, disappear, shade 黒 – black
Four-Kanji Jukugo: Yojijukugo 四字熟語
As a bonus, lets look at the famous yojijukugo 四字熟語. As the name suggests, they are four-kanji jukugo, but the term yojijukugo is especially used in reference to set idiomatic expressions of this type. For more information and a long list of yojijukugo, I recommend you review Imabi’s resource. But just for fun, let’s look at a few examples. One thing you’ll find with the examples below is that they are really just two-kanji jukugo stuck together.
Yojijukugo examples: 老若男女 Reading: ろうにゃくなんにょ, rounyakunannyo Meaning: people of all ages Decomposition: 老若 – young and old 男女 – men and women 紆余曲折 Reading: うよきょくせつ, uyokyokusetsu Meaning: twists and turns. Often used when people say that they went through an experience containing many twists and turns before finally arriving at a resolution or an endpoint. “After many twists and turns…”, 「紆余曲折を経て。。。」. Decomposition: 紆余 – meandering, winding 曲折 – twists and turns, complications, difficulties 本末転倒 Reading: ほんまつてんとう, honmatsutentou Meaning: focusing on the trivial and ignoring the essential. Getting one’s priorities backwards. 本末 – essence and fringe, beginning and ending, means and end 転倒 – overturning, inverting, reversing
References:
[1] Wikipedia contributors. 合成語. In Wikipedia, The Free Encyclopedia. Jan. 2023. https://ja.wikipedia.org/wiki/合成語
[2] Mori, Yoshiko. (2012). Five myths about kanji and kanji learning. Japanese Language and Literature, 46, 1. https://www.jstor.org/stable/41442049
[3] Taeko Ogawa, Hirofumi Saito. Semantic Activation in Visual Recognition of Japanese Two-kanji Compound Words: Interference and Facilitatory Effects of Neighbors. Psychologia, 2006, 49, 162–177. https://www.jstage.jst.go.jp/article/psysoc/49/3/49_3_162/_article
Works Consulted:
[1] Wikipedia contributors. 熟語. In Wikipedia, The Free Encyclopedia. Jan. 2023. https://ja.wikipedia.org/wiki/熟語
[2] Benesse Corporation. 国語: 熟語の構成. 進研ゼミ小学講座. Jan. 2023. https://sho.benesse.co.jp/qat/j/15.html
[3] 対崎正宏. 熟語の構成 一覧（あいうえお順）組み立てから分類. 対崎正宏 OFFICIAL WEB SITE. Jan. 2023. https://tsuizakimasahiro.com/two-letter-phrase-example/
[4] まいにちマナブ Manab. 中学国語「二字熟語の構成（組み立て）」種類と例・問題まとめ. Jan. 2023. https://manab-juku.me/japanese/jukugo-kosei/