Meaning
剛 means strong, hard, firm, and unyielding — but with a precise edge. Where 強 is a general word for power, 剛 names something harder: strength that will not bend under pressure. Think of a tempered blade, an iron will, a warrior who holds the line without flinching. It is not just force, but the refusal to yield.
剛 is a phono-semantic compound (形声文字). On the right, 刂 (りっとう) — a variant of 刀 meaning "blade" or "sword" — supplies the semantic core: sharpness, hardness, cutting force. On the left, 岡 contributes the reading ゴウ. Together they picture a sword that never dulls — inherently hard and resolute.
At 10 strokes, 剛 is a Joyo kanji assigned to the secondary education level (grade 8, taught in junior high and high school). Its literary, formal register explains its JLPT N1 placement. You will rarely hear it in casual speech. Look for it instead in martial arts writing, sports journalism, literary prose, and business contexts where decisive leadership is being praised.
One phrase captures the spirit of 剛 perfectly: 外柔内剛 — gentle on the outside, unyielding within. This ideal runs deep in Japanese culture. The most admired leaders and warriors are often described this way: strength hidden beneath a composed exterior, the iron fist in the velvet glove.
Readings
On'yomi (音読み) — Chinese-derived readings
剛 has one on'yomi: ゴウ (Gō). It appears in virtually every compound containing this kanji and is never used in isolation to mean "strong." All of 剛's vocabulary comes through the compounds it forms.
Five compounds worth learning early:
- 剛力 (gōriki) — extraordinary physical strength; historically, a person hired for heavy labor due to great strength
- 剛健 (gōken) — robust, hardy, and vigorous in both body and spirit
- 剛毅 (gōki) — resolute, firm, and unyielding in character
- 剛腕 (gōwan) — a powerful arm; metaphorically, a forceful and capable leader
- 剛速球 (gōsokkyū) — a blazing fastball in baseball
Kun'yomi (訓読み) — Native Japanese readings
剛 has no standard kun'yomi in modern Japanese. In archaic literary texts it occasionally takes the reading つよ (tsuyo) as a variant of 強, but this usage is rare and does not appear in JLPT testing. One fixed exception: 剛者 (tsuwamono), meaning "a brave warrior" or "a formidable person," survives as a set classical term preserved from classical literature.
For JLPT N1, ゴウ is the only reading that matters. There is no productive kun'yomi pattern to internalize for this kanji.
Common Words & Compounds
These compounds cover 剛 across its main domains — moral character, physical power, engineering, and classical expression.
Strength of Character & Moral Fortitude
- 剛毅 (gōki) — resolute and unyielding; iron will; unwavering determination in the face of adversity
- 剛直 (gōchoku) — upright and honest; a straightforward person who will not bend their principles
- 剛胆 (gōtan) — bold, daring, and audacious; brave without recklessness
- 剛勇 (gōyū) — brave and mighty; the quality of a great warrior combining strength and courage
Physical Power & Vitality
- 剛力 (gōriki) — extraordinary physical strength; the power to lift or move what others cannot
- 剛健 (gōken) — robust, hardy, and vigorous; peak physical and mental condition
- 剛腕 (gōwan) — powerful arm; in modern usage, a politician or executive with a forceful, decisive style
- 剛速球 (gōsokkyū) — a blazing fastball; a pitch thrown with maximum speed
Technical & Scientific Usage
- 剛性 (gōsei) — rigidity, stiffness; a materials science and engineering term for resistance to deformation under load
Classical Expressions & Set Phrases
- 外柔内剛 (gaijūnaigō) — outwardly gentle, inwardly strong; the iron fist in a velvet glove; a highly valued personality ideal in Japanese culture
- 剛柔 (gōjū) — hard and soft; a pairing central to martial arts philosophy (e.g., 剛柔流, a major karate style from Okinawa)
- 剛者 (tsuwamono) — a brave warrior; a formidable person; a classical literary term
Example Sentences
あの選手は剛力で知られ、他の誰にも真似できない投球をする。
Ano senshu wa gōriki de shirare, hoka no dare ni mo mane dekinai tōkyū wo suru.
That athlete is known for his extraordinary strength and throws in a way no one else can replicate.
剛健な精神を育てるには、日々の鍛錬が欠かせない。
Gōken na seishin wo sodateru ni wa, hibi no tanren ga kakasenai.
Daily training is indispensable for cultivating a robust and vigorous spirit.
あの投手の剛速球は、打者たちを次々と圧倒した。
Ano tōshu no gōsokkyū wa, dashatachi wo tsugitsugi to attō shita.
That pitcher's blazing fastball overwhelmed the batters one after another.
この素材は剛性が非常に高く、極端な圧力にも変形しない。
Kono sozai wa gōsei ga hijō ni takaku, kyokutan na atsuryoku ni mo henkei shinai.
This material has extremely high rigidity and does not deform even under extreme pressure.
その女性リーダーは外柔内剛で、部下から深く信頼されている。
Sono josei rīdā wa gaijūnaigō de, buka kara fukaku shinrai sarete iru.
That female leader is gentle on the outside but strong on the inside, and is deeply trusted by her subordinates.
剛毅な意志を持つ者だけが、この試練を乗り越えることができる。
Gōki na ishi wo motsu mono dake ga, kono shiren wo nori koeru koto ga dekiru.
Only those with a resolute and unyielding will can overcome this trial.
その政治家は剛腕ぶりで難局を打開し、国民の支持を集めた。
Sono seijika wa gōwan-buri de nankyoku wo dakai shi, kokumin no shiji wo atsumeta.
That politician broke through the difficult situation with his forceful leadership and gathered the support of the people.
剛直な性格の彼は、上司の命令でも間違っていると思えば従わない。
Gōchoku na seikaku no kare wa, jōshi no meirei demo machigatte iru to omoeba shitagawanai.
Because of his upright and principled character, he will not obey even his superior's orders if he believes they are wrong.
剛柔流は沖縄を発祥の地とする伝統的な空手の流派である。
Gōjūryū wa Okinawa wo hasshō no chi to suru dentōteki na karate no ryūha de aru.
Gōjū-ryū is a traditional style of karate that originated in Okinawa.
剛胆な船長は、嵐の中でも冷静を保ち、乗組員を率いた。
Gōtan na senchō wa, arashi no naka demo reisei wo tamochi, norikumiin wo hiita.
The bold captain remained calm even in the storm and led the crew.
Memory Tip
Split 剛 into its parts: a sword (刂) on a ridge (岡). That blade stands at the peak, exposed to every storm — and it does not bend. The image carries the meaning directly.
For the reading: ゴウ lands hard and final, like something that will not give way. The sound suits the character.
Pair 剛 against its opposite, 柔 (soft, yielding), through the phrase 外柔内剛. The contrast locks both kanji in place at once. Soft outside, hard inside — once that image is set, 剛 does not fade.