Meaning
The kanji 械 carries the core meanings of machine, mechanism, contraption, and — in its oldest sense — fetters or wooden shackles. In contemporary Japanese, it appears almost exclusively in compound words relating to machines, instruments, and mechanical devices. Yet its historical root is worth knowing: it reveals why the character looks the way it does and makes it far easier to remember.
Etymologically, 械 is a compound ideograph built from two elements. 木 (ki/moku — wood, tree) sits on the left as the semantic radical. 戒 (kai — commandment, warning, restraint) stands on the right, supplying both the phonetic hint and a layer of meaning. Together they evoke the image of a wooden restraining device — in ancient China and Japan, shackles and stocks used to bind prisoners were made from wood. The compound meaning is literally "a wooden thing that controls or restrains." As technology advanced and wooden mechanisms gave way to metal and steam, the meaning of 械 expanded to cover all manner of mechanical devices.
This kanji has 11 strokes and is classified as a secondary school kanji (中学校配当漢字), standard for the JLPT N2 level. Its radical is 木 (tree/wood), which connects it to a large family of kanji involving crafted objects, tools, and natural materials. In modern usage, 械 almost never stands alone — it lives inside compounds. The most common is 機械 (machine, machinery), a word you will encounter everywhere from factory floors to AI research papers.
Readings
On'yomi (音読み) — Chinese-derived readings
The kanji 械 has one primary on'yomi reading: カイ. Derived from the Middle Chinese pronunciation, this reading appears almost exclusively in compound words (jukugo, 熟語). You will encounter カイ in both formal and casual contexts — technology, engineering, science, and physical education all draw on it regularly.
- 機械 (kikai) — machine, machinery (the most common compound; refers to any machine or mechanical system)
- 器械 (kikai) — instrument, apparatus, device (commonly used for gymnastics equipment or medical instruments; note the different first kanji 器 vs 機)
- 機械的 (kikaiteki) — mechanical, automatic, robot-like (used both literally for machines and figuratively to describe repetitive or unthinking behavior)
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi reading of 械 is かせ, referring specifically to wooden fetters, shackles, or stocks historically used to restrain a person's hands or feet. Archaic and essentially absent from modern standard Japanese, it surfaces in classical literature, historical dramas (jidaigeki), or academic discussions of traditional Japanese legal punishment. For N2 purposes, treat かせ as historical color rather than active vocabulary.
- 械 (kase) — fetters, shackles, wooden restraints (archaic; historical and classical usage only)
Since 械 has no commonly used kun'yomi in contemporary Japanese, concentrate on the on'yomi カイ and the compound words built around it.
Common Words & Compounds
One on'yomi, but a wide range of compounds. 械 turns up across technology, industry, engineering, and everyday life in Japan — these words are worth knowing well beyond the exam.
Core everyday compounds:
- 機械 (kikai) — machine, machinery (general term for any machine; appears in nearly every industrial or scientific context)
- 器械 (kikai) — instrument, apparatus (used for gymnastic equipment in PE class, or medical/scientific instruments)
- 機械的 (kikaiteki) — mechanical, automatic (describes both literal machine operation and figurative "robotic" human behavior)
- 機械化 (kikaika) — mechanization (the process of replacing human or animal labor with machines)
Industry and engineering:
- 機械工学 (kikai kōgaku) — mechanical engineering (a major university faculty and professional discipline)
- 機械工 (kikaiko) — machinist, machine operator (a person who operates or maintains industrial machinery)
- 精密機械 (seimitsu kikai) — precision machinery, precision instruments (e.g., watches, medical scanners)
- 農業機械 (nōgyō kikai) — agricultural machinery (tractors, harvesters, etc.)
Modern and digital contexts:
- 機械学習 (kikai gakushū) — machine learning (core AI/ML terminology; very common in tech news and academic papers)
- 機械翻訳 (kikai hon'yaku) — machine translation (automated language translation systems such as neural MT engines)
Example Sentences
この工場には最新の機械が導入されています。
Kono kōjō ni wa saishin no kikai ga dōnyū sarete imasu.
The latest machinery has been introduced into this factory.
機械の使い方を教えてもらえますか。
Kikai no tsukaikata wo oshiete moraemasu ka.
Could you teach me how to use this machine?
この器械は体育の授業でよく使います。
Kono kikai wa taiiku no jugyō de yoku tsukaimasu.
We often use this apparatus in physical education class.
機械的に作業をこなすのではなく、創意工夫が大切だ。
Kikaiteki ni sagyō wo konasu no de wa naku, sōi kufū ga taisetsu da.
Rather than completing tasks mechanically, creativity and ingenuity are what matter.
農業の機械化により、労働力が大幅に削減された。
Nōgyō no kikaika ni yori, rōdōryoku ga ōhaba ni sakugen sareta.
Due to the mechanization of agriculture, the need for manual labor was drastically reduced.
機械学習は人工知能の重要な分野の一つです。
Kikai gakushū wa jinkō chino no jūyō na bun'ya no hitotsu desu.
Machine learning is one of the important fields within artificial intelligence.
精密機械の製造には高度な技術が必要です。
Seimitsu kikai no seizō ni wa kōdo na gijutsu ga hitsuyō desu.
High-level technical skills are required for manufacturing precision instruments.
彼は機械工学を専攻していて、卒業後は自動車会社に就職した。
Kare wa kikai kōgaku wo senkō shite ite, sotsugyō go wa jidōsha gaisha ni shūshoku shita.
He majored in mechanical engineering and got a job at an automobile company after graduation.
機械翻訳は便利ですが、まだ専門家の翻訳には及びません。
Kikai hon'yaku wa benri desu ga, mada senmonka no hon'yaku ni wa oyobimasen.
Machine translation is convenient, but it still does not match the work of a professional translator.
Memory Tip
Think of 械 as a wooden warning device. Break it into its two parts: 木 (tree, wood) on the left — the material it is made from — and 戒 (commandment, warning, restraint) on the right — what it is used for. Picture an ancient wooden contraption: a heavy stock used to lock a prisoner's neck and wrists in the town square. Wood (木), built to restrain (戒). From that image of control and structure, the meaning grew naturally into the modern world — today's machines are still devices built to control and process materials, energy, and information. Every time you sit at a computer or ride in a car, you are using a descendant of that first wooden 械. Wood + warning = a device that controls.