長い・永い|ながいnagai[2]nakadaka (mid-high)

1. i-adjectivelong (distance, length)
   彼かれに長ながい手紙てがみを書かいた。↗

   I wrote a long letter to him.

   これは日本にっぽんで２番目ばんめに長ながい川かわだ。↗

   This is the second longest river in Japan.
2. i-adjectivelong (time); protracted; prolonged
   株式市場かぶしきしじょうは長ながい不振ふしんを続つづけている。↗

   The stock market is in a prolonged slump.

   だんだん日ひが長ながくなっています。↗

   The days are getting longer and longer.

• Related限りないかぎりないWrittenWritten and lyrical for something boundless or unlimited, as in 「限りない愛」; carries an emotive, emphatic tone that 「長い」 lacks.
• Related果てしないはてしないNeutralNeutral word for something endless or boundless, as in 「果てしない宇宙」; stresses there is no end, which 「長い」 does not.
• Related長期的ちょうきてきNeutralMeans long-term, viewing things over an extended span, as in 「長期的な視点」; typical of plans and analysis, not physical length.
• Related永久えいきゅうNeutralMeans lasting forever with no end, as in 「永久に保存」; 「長い」 covers mere length or duration, not permanence.
• RelatedはるかNeutralFor distances or stretches of time far removed, as in 「遥か昔」; stresses remoteness rather than length, the domain of 「長い」.
• RelatedエンドレスNeutralLoanword for something endless or looping on without a stop, as in 「エンドレスに続く」; casual nuance, unlike plain 「長い」.
• Related程遠いほどとおいNeutralFor being far off in distance or time, and also far from a goal, as in 「完成には程遠い」; 「長い」 does not cover falling short.
• Related久しいひさしいWrittenWritten word for a long time having passed, as in 「久しく会っていない」; applies to elapsed time only, never physical length.
• Related遠いとおいNeutralFor distance between two places or remoteness in time; stresses separation, while 「長い」 measures length or duration.
• Related長長しいながながしいWrittenWritten style for something long and drawn-out, with a tinge of annoyance, as in 「長々しい挨拶」; 「長い」 simply states length.
• Related止めどないとめどないWrittenWritten word for something ceaseless that keeps flowing or coming without stopping, as in 「止めどなく涙が流れる」; stresses that it will not let up.
• Related果てしがないはてしがないWrittenSame meaning as 「果てしない」: no end, stretching on without limit. 「長い」 only says something is long, not that it never ends.
• RelatedきりのないCasualColloquial for something that goes on and on with no end in sight, as in 「言い出したら切りがない」, often with a resigned, exasperated feel.
• Related長たらしいながたらしいCasualColloquial and negative for talk or writing that is annoyingly long, as in 「長ったらしい説明」; 「長い」 is neutral about length.
• Related常しなえとこしなえWrittenArchaic, literary word for what continues unchanged forever; found mainly in poetry and elevated prose, not everyday speech.
• Related半永久的はんえいきゅうてきNeutralMeans nearly permanent though not truly eternal, as in 「半永久的に使える」; used of objects and states, a nuance 「長い」 does not cover.
• Related無窮むきゅうWrittenWritten word for infinity without end in time or space, as in 「天壌無窮」; literary and not used in daily conversation.
• Related永続的えいぞくてきWrittenWritten-style word for a state that lasts or persists, as in 「永続的な平和」; about endurance of a state, not physical length.
• Related長期にわたるちょうきにわたるWrittenVerb phrase for something continuing over a long period, as in 「長期にわたる交渉」; common in news and reports.
• Antonym短いみじかいNeutralDirect antonym of 「長い」: short in length or brief in time.
• Antonym一瞬のNeutralAntonym of 「長い」 in its time sense: lasting only an instant, extremely brief.

Use 「長い」 by default for length and duration. For something tediously long pick 「長たらしい」; for endlessness 「果てしない」 or 「限りない」; for permanence 「永久」; for far-off distance 「遠い」; for a long-term outlook 「長期的」. The rest are narrower: literary, colloquial, or specialized takes on the same ideas.

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

1. 距離きょりが離はなれている様さま。両端りょうたんの隔へだたりが大おおきいさま。
2. 時間じかんが多おおくかかる様さま。
3. 根気こんきのいるさま。のんびりしたさま。
4. 訪問先ほうもんさきに長時間ちょうじかん逗留とうりゅうすること。通常つうじょう、訪問ほうもん相手あいてが迷惑めいわくを感かんじている（または、感かんじるであろうことを見越みこす）ニュアンスを含ふくむ。