約|やくyaku[1]atamadaka (head-high)

1. adverbapproximately; about
   その値段ねだんは約やく５０ドルだった。↗

   The price was in the neighbourhood of 50 dollars.
2. nounpromise; appointment; engagement
3. nounshortening; reduction; simplification
4. noun, linguisticscontraction (in phonetics)

• SynonymほぼNeutralCovers 'almost, nearly' (「ほぼ完成」「ほぼ同じ」); 「約」 is for approximate amounts and mostly attaches to numbers.
• SynonymおよそNeutralMeans 'about, roughly' (「およそ百人」), and with a negative 'not at all'; slightly more formal than 「約」.
• SynonymざっとCasualColloquial: for rough estimates (「ざっと見積もる」) and for going over something briefly.
• RelatedほとんどNeutralMeans 'almost, mostly' (「ほとんど終わった」); with a negative it means 'hardly, scarcely'.
• RelatedおおよそNeutralMeans 'roughly, on the whole' (「おおよその見当」) and often modifies a noun; 「約」 mostly attaches to numbers, as in 「約半分」.
• Related粗々あらあらWrittenWritten style for 'roughly, broadly'; rare today, kept in the letter closing 「あらあらかしこ」.
• Related無慮むりょWrittenWritten style for 'as many as roughly' a large number (「無慮数万」); attaches only to large figures and is rare.
• Antonym正確せいかくNeutralMeans 'accurate, free of error', the opposite of the approximation expressed by 「約」.
• Antonym厳密げんみつWrittenA written-style word meaning 'strict, precise' (「厳密に言えば」), contrasting with 「約」's roughness.

Use 「約」 before numbers for approximate amounts (「約3時間」). In speech, 「だいたい」 and 「ざっと」 are the natural choices. Use 「ほぼ」 for nearly complete and 「ほとんど」 for almost all; 「おおよそ」 suits rough estimates. The opposites are 「正確」 and 「厳密」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. (ヤク) 約束やくそくすること。とりきめ。誓ちかい。
2. (ヤク) 縮ちぢめたもの。短縮たんしゅくすること。
3. (ヤク) 約音やくおんの略称りゃくしょう。
4. (ヤク) 大体だいたいの数量すうりょうであること。およそ。ほぼ。