Meaning
勢 covers a broad range of meanings: force, power, energy, momentum, and influence. Unlike simple words for strength, it captures the flowing, unstoppable quality of energy in motion — momentum that builds on its own and becomes hard to stop. You'll find it in dynamic situations, political writing, descriptions of natural forces, and expressions of personal vitality.
勢 has two main parts. The upper component 埶 shows a person cultivating or planting — skill and controlled action. Below it sits the radical 力 (ちから), meaning "power" or "force." Together they describe power that is directed, not random. That's why 勢 covers everything from military might to the drift of the times.
勢 has 13 strokes and is taught in Grade 6. It shows up constantly in news, business writing, and literature — a must-know at N2. Vietnamese learners get a head start: the Hán-Việt reading THẾ maps directly to thế lực (power/influence) and hình thế (situation/state).
Readings
On'yomi (音読み) — Chinese-derived readings
The main on'yomi is セイ. It appears almost entirely in Chinese-derived compounds (jukugo) and dominates formal writing — politics, military, and science above all.
- 勢力 (seiryoku) — power, influence, force (a typhoon's force; a political faction's clout)
- 形勢 (keisei) — situation, state of affairs, how things stand
- 情勢 (jōsei) — current situation, circumstances
- 優勢 (yūsei) — predominance, superiority, being in the lead
- 劣勢 (ressei) — inferiority, being at a disadvantage
- 運勢 (unsei) — fortune, luck, one's fate (common in horoscopes)
- 威勢 (isei) — power, authority, vigor, high spirits
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi is いきおい. As a standalone noun, it captures natural, organic momentum: the rush of a river, the energy of a crowd, a trend that won't slow down. It carries a physical, visceral weight that the on'yomi compounds lack.
- 勢い (ikioi) — force, vigor, impetus, momentum
- 勢いよく (ikioi yoku) — vigorously, with great force (adverbial)
- 勢いづく (ikioizuku) — to gain momentum, to be invigorated
Common Words & Compounds
勢 turns up across politics, nature, military contexts, and daily life. Here are the key compounds, grouped by theme.
Power and Influence
- 勢力 (seiryoku) — power, influence, force
- 権勢 (kensei) — power and influence, authority
- 勢力圏 (seiryokuken) — sphere of influence
- 威勢 (isei) — vigor, high spirits, power
Situation and Trends
- 形勢 (keisei) — situation, state of affairs
- 情勢 (jōsei) — current situation, circumstances
- 時勢 (jisei) — the trend of the times, the current of events
- 大勢 (taisei) — general trend, the tide of events
People and Groups
- 大勢 (ōzei) — large number of people, a crowd (same kanji, different reading and meaning)
- 軍勢 (gunzei) — military force, troops, army
- 多勢 (tazei) — large number, large force (often in 多勢に無勢)
Position and Posture
- 体勢 (taisei) — posture, stance, body position
- 態勢 (taisei) — readiness, attitude, posture (preparatory stance)
- 姿勢 (shisei) — posture, attitude, stance (physical and metaphorical)
Advantage and Disadvantage
- 優勢 (yūsei) — predominance, superiority
- 劣勢 (ressei) — inferiority, being at a disadvantage
- 攻勢 (kōsei) — offensive (military or figurative)
Example Sentences
川の水が勢いよく流れている。
Kawa no mizu ga ikioi yoku nagarete iru.
The river water is flowing with great force.
チームは勢いに乗って連勝した。
Chīmu wa ikioi ni notte renshō shita.
The team rode the momentum and won game after game.
この地域では反対派の勢力が強い。
Kono chiiki de wa hantaiha no seiryoku ga tsuyoi.
In this region, the opposition holds real power.
今年の運勢は悪くないらしい。
Kotoshi no unsei wa warukunai rashii.
Apparently this year's fortune isn't looking bad.
試合の形勢は徐々に逆転した。
Shiai no keisei wa jojo ni gyakuten shita.
The tide of the match slowly turned.
世界の情勢は刻々と変化している。
Sekai no jōsei wa kokkoku to henka shite iru.
The world situation is shifting by the minute.
彼は威勢のいい声で返事をした。
Kare wa isei no ii koe de henji wo shita.
He answered in a loud, spirited voice.
多勢に無勢で、勝てる見込みはなかった。
Tazei ni buzei de, kateru mikomi wa nakatta.
Badly outnumbered, they had no real chance of winning.
新しい技術が勢いを増している。
Atarashii gijutsu ga ikioi wo mashite iru.
New technology is gaining momentum.
選手たちは攻勢に出て点数を稼いだ。
Senshu-tachi wa kōsei ni dete tensū wo kaseida.
The players went on the offensive and racked up points.
Memory Tip
Picture a warrior (力) who has spent years cultivating his skills (the upper component 埶, a person tending the earth). He doesn't rush — he builds his power quietly, and when he finally moves, nothing stops his 勢い. A dam filling behind a wall works the same way: the force doesn't appear all at once, but once it breaks, the ikioi is absolute. That image of accumulated, directed power is what 勢 is about.
Vietnamese learners: the Hán-Việt reading THẾ maps straight to thế lực (势力) — power and influence, exactly as in Japanese.