長い間・長いあいだ・ながい間|ながいあいだnagaiaida

1. expression, noun, adverblong time; long interval; for quite some time
   これは私が長ながい間あいだ欲ほしかったものだ。↗

   This is what I've long wanted.

• Synonym長年ながねんNeutralMany years, as in 「長年の夢」, emphasizing the length in years; 「長い間」 is not limited to spans counted in years.
• Synonym長らくながらくNeutralLong; much used in greetings and speeches, as in 「長らくお待たせしました」.
• Synonym長々ながながNeutralAt length or long-windedly, as in 「長々と話す」「長々と横になる」, sometimes with a nuance of impatience.
• Synonym長期ちょうきNeutralLong-term; rather formal, as in 「長期休暇」, and mostly used in compounds.
• Synonym長期間ちょうきかんNeutralA long period; formal and written-leaning, as in 「長期間の保存」.
• Synonym永年えいねんWrittenThe same word as 長年, read 「ながねん」; also written 「永年」. Many years; 「長い間」 is not limited to years. The 「永年」 spelling is the more written form.
• Related年月としつきNeutralThe months and years, as in 「長い年月をかけて」, with a feel of time flowing by.
• Related多年たねんWrittenMany years; written and rather formal, as in 「多年の功績」.
• Related積年せきねんWrittenMany years piling up; written, as in 「積年の恨み」, usually with a negative nuance.
• Related長日月ちょうじつげつWrittenA long stretch of time; written and old-fashioned, rare in everyday use; 「長い年月」 is the usual way to say it.
• Antonym一瞬いっしゅんNeutralAn instant, the blink of an eye; the opposite of 「長い間」 for a very long span.
• Antonym短い間NeutralA short period of time; the opposite of 「長い間」, and not a fixed expression.

For everyday talk about a long time, use 「長い間」, as in 「長い間お世話になりました」. For many years say 「長年」; in greetings or speeches say 「長らく」. 「長期」 and 「長期間」 are formal terms for long spans; 「多年」, 「永年」 and 「積年」 suit written prose; 「年月」 evokes the passing of time; 「長々」 describes drawn-out actions; 「長日月」 is old-fashioned. Antonyms: 「短い間」, 「一瞬」.

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

1. 多おおくの時間じかんが経たつこと。かなりの期間きかん。