一円|いちえんichien[0]heiban (flat)

1. nounone yen
   １円えんたりとも無駄使むだづかいはできない。↗

   I can't afford to waste a single yen.
2. suffix, adverbthroughout (an area); whole district

• Synonym一切いっさいWrittenWritten/formal prose; means 'all, everything', and with a negative 'none whatsoever'; 「一円」 leans toward the geographic whole of a region, as in 「関東一円」.
• RelatedまるっきりCasualColloquial adverb, mostly before a negative for 'not at all, not in the least'; 「一円」 is now mainly a noun for the whole of an area, as in 「関東一円」.
• Related一向いっこうWrittenIn written or formal prose, mostly as 「一向に〜ない」 for 'not at all, not the least'; 「一円」 no longer works as a negative adverb and mainly means a whole district.
• RelatedまるでNeutralNeutral adverb: with a negative it means 'not in the slightest', and it also covers 'as if, just like'; 「一円」 has no such figurative use and points to a whole region.
• RelatedまったくNeutralNeutral adverb: 'completely', with a negative 'not at all', and it can even serve as an exclamation; 「一円」 mainly covers a whole area.
• RelatedまんざらCasualColloquial; mostly as 「満更でもない」, 'not entirely so — actually quite pleased'; 「一円」 instead means the whole of a region.
• Related何もなにもNeutralNeutral; with a negative it means 'nothing at all', and it also covers 'there's no need to go that far', as in 「何もそこまで」; 「一円」 means a whole region.
• Related全然ぜんぜんCasualEveryday colloquial adverb, mostly with a negative for 'not at all'; in speech it can also mean 'very'; 「一円」 is a noun for an area.
• Related根っからねっからCasualColloquial; means 'by nature, at heart', as in 「根っからの商人」, and with a negative 'not at all'; 「一円」 covers the whole of an area.
• Related皆目かいもくWrittenWritten/formal prose adverb; with a negative it means 'not at all, not the slightest', as in 「皆目わからない」; 「一円」 denotes a whole area.
• RelatedさっぱりCasualColloquial; mostly 'refreshed, neat, frank', but with a negative also 'not at all', as in 「さっぱりわからない」; 「一円」 means a whole area.
• RelatedからっきしCasualColloquial adverb; with a negative it means 'utterly, not at all', as in 「からっきし駄目だ」; 「一円」 denotes a whole area.
• RelatedまるきりCasualColloquial adverb, a synonym of 「丸っきり」; with a negative it means 'not at all'; 「一円」 is a noun for a whole district.
• RelatedとんとWrittenWritten/formal prose adverb: 'completely, not in the least', mostly with a negative, as in 「とんと見ない」; 「一円」 refers to an area as a whole — a different use.

Use 「一円」 for the whole of a region, as in 「関東一円」. For 'completely not' with a negative, pick 「全く」, 「全然」 or 「まるで」; in written or formal prose 「一向に」 and 「皆目」; for 'all, everything' use 「一切」.

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

1. 全すべて。総体そうたい。
2. ある区域くいきの全体ぜんたい。一帯いったい。全域ぜんいき。
3. 日本にっぽん国こくの通貨つうか単位たんい「円えん」の一ひとつ分ぶん。一いち銭せんの百ひゃく倍ばい。
4. 尽ことごとく。全すべて残のこらず。
5. （打ち消うちけしの語ごを伴ともなって）更さらに。全然ぜんぜん。
6. 無住むじゅうの号ごう。