積年|せきねんsekinen[0]heiban (flat)

1. noun(many) years
2. no-adjectivelong-standing (esp. hatred, grudge); ancient

• Synonym長年ながねんNeutralThe most general word for many years, as in 「長年の夢」. 「積年」 is more written in tone and usually speaks of grudges or abuses piled up over the years.
• Synonym多年たねんWrittenWritten/formal word for many years, as in 「多年にわたる研究」「多年の経験」; more formal than 「長年」. It carries none of 「積年」's sense of accumulated grudges or abuses.
• Synonym長期ちょうきNeutralMeans long-term, as in 「長期計画」; it concerns the length of a planned term and says nothing of things built up over the years.
• Synonym永年えいねんNeutralAnother way of writing 「長年」; often seen in commendations such as 「永年勤続」. Like 「長年」, it has none of 「積年」's grudge-laden nuance.
• Related年月としつきNeutralMeans the months and years, as in 「年月が経つ」; it leans toward the passing of time and never speaks of grudges or abuses built up over the years.
• Related長い間ながいあいだNeutralColloquial and the plainest way to say a long time; it is not tied to whole years, unlike 「積年」, which speaks only of many years.
• Related長期間ちょうきかんWrittenWritten/formal term for a long period; it describes the length of a span objectively and carries no sense of accumulation.
• Related長日月ちょうじつげつWrittenWritten/formal word for long stretches of time, now rarely used; it lacks 「積年」's nuance of grudges or abuses accumulated over years.
• Antonym短期たんきNeutralMeans short-term; it stands at the opposite pole from the many-year accumulation that 「積年」 describes.

For plain 'many years,' use 「長年」. In written style, for grudges or abuses built up over many years, use 「積年」, as in 「積年の恨み」「積年の課題」. For the length of a term or period, choose 「長期」 or 「短期」.

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

1. 長ながい年月としつき。