Meaning
約 has two main uses. Before numbers, it means approximately — the Japanese equivalent of "about" or "around." In social and legal contexts, it means a promise, vow, or binding agreement. Formal documents extend this further to contract or treaty. One additional meaning, confined to mathematics, is to simplify or reduce a fraction.
The left side is the radical 糸 (いと, thread/silk). The right side, 勺 (ヤク), supplies the reading. Thread suggests binding — promises bind people to their word, and "approximately" pins a vague number to something workable. That shared quality of loosely but deliberately fastening something down runs through every sense of 約.
九画 (9 strokes), Grade 4 Jōyō kanji — Japanese children encounter it around age 10. For N3 learners, 約 turns up in job contracts, restaurant bookings, election pledges, and everyday conversation. It earns its study time.
Readings
On'yomi (音読み) — Chinese-derived reading
One on'yomi: ヤク. It covers virtually every compound this character appears in, from diplomatic treaties to coffee shop reservations.
- 約束 (yakusoku) — promise, appointment
- 予約 (yoyaku) — reservation, advance booking
- 契約 (keiyaku) — contract, agreement
- 条約 (jōyaku) — treaty (between nations)
- 節約 (setsuyaku) — saving, economizing
- 制約 (seiyaku) — restriction, constraint
- 公約 (kōyaku) — public pledge, campaign promise
- 約分 (yakubun) — reduction of a fraction (mathematics)
ヤク stays consistent whether the subject is a summit treaty, a lunch reservation, or a math problem. Once you know this sound, you'll recognize 約 compounds on sight.
Kun'yomi (訓読み) — Native Japanese reading
No active kun'yomi in modern Japanese. The verb 約する (やくする, "to promise / to abbreviate") surfaces occasionally in literary and legal writing, but not in speech. For the JLPT N3 and real-world use, the ヤク compounds above are what matter.
Common Words & Compounds
Promises & Agreements
- 約束 (yakusoku) — promise, appointment, commitment
- 契約 (keiyaku) — contract, formal agreement
- 条約 (jōyaku) — treaty (between countries)
- 公約 (kōyaku) — public pledge, political promise
- 誓約 (seiyaku) — oath, sworn promise
Approximation & Quantity
- 約 (yaku) — approximately, about (standalone)
- 概約 (gaiyaku) — outline, rough summary
- 大約 (taiyaku) — roughly, in broad terms
Reservations & Scheduling
- 予約 (yoyaku) — reservation, pre-order, booking
- 予約済 (yoyakuzumi) — already reserved, booked
Restriction & Economy
- 節約 (setsuyaku) — saving, frugality
- 制約 (seiyaku) — restriction, limitation
Mathematics
- 約分 (yakubun) — reduction of a fraction
- 約数 (yakusū) — divisor, factor
Example Sentences
約10分で着きます。
Yaku juppun de tsukimasu.
I'll be there in about 10 minutes.
友達と約束があります。
Tomodachi to yakusoku ga arimasu.
I have plans with a friend.
レストランを予約しました。
Resutoran wo yoyaku shimashita.
I made a reservation at the restaurant.
約束を守ることが大切です。
Yakusoku wo mamoru koto ga taisetsu desu.
Keeping your word matters.
節約のために、毎日お弁当を作っています。
Setsuyaku no tame ni, mainichi obentō wo tsukutte imasu.
I pack a bento every day to cut costs.
この会社は約500人の従業員がいます。
Kono kaisha wa yaku gohyaku nin no jūgyōin ga imasu.
This company has around 500 employees.
契約の内容をよく読んでください。
Keiyaku no naiyō wo yoku yonde kudasai.
Read the contract terms carefully before signing.
両国は新しい条約に署名した。
Ryōkoku wa atarashii jōyaku ni shomei shita.
The two countries signed a new treaty.
制約の中で最善を尽くすことが大事だ。
Seiyaku no naka de saizen wo tsukusu koto ga daiji da.
Do your best within whatever constraints you face.
政治家は選挙の公約を果たすべきだ。
Seijika wa senkyo no kōyaku wo hatasu beki da.
Politicians should follow through on their campaign promises.
Memory Tip
Focus on the 糸 (thread) radical on the left. Thread binds things together. A promise binds people to their word. "Approximately" binds a vague number to something concrete. Both meanings of 約 share that same quality — something loosely but deliberately fastened. Spot the thread, think binding, and the meaning follows.