永遠|えいえんeien[0]heiban (flat)

1. no-adjective, na-adjectiveeternity; perpetuity; permanence; immortality
   その画家がかは、いわば永遠えいえんの少年しょうねんだ。↗

   The artist is eternally a boy.

• Synonym永久えいきゅうNeutralObjective and practical rather than lyrical: no end in time, as in 「永久歯」 or 「永久保存」. 「永遠」 carries more emotional weight.
• Synonym不滅ふめつWrittenEmphasizes being indestructible—never perishing or fading, as in 「不滅の記録」. 「永遠」 stresses endless time instead.
• Synonym恒久こうきゅうWrittenLong and unchanging, used mainly for peace and institutions, as in 「恒久平和」. More written and objective than 「永遠」.
• Synonym永世えいせいWrittenPermanence, used in titles and fixed phrases like 「永世中立」 and 「永世名人」. Less versatile than 「永遠」.
• Synonym永代えいたいWrittenPermanence, used for memorial services and usage rights, as in 「永代供養」. Less versatile than 「永遠」.
• Synonym長久ちょうきゅうWrittenLong duration, seen in congratulatory phrases like 「武運長久」. Less absolute in degree than 「永遠」.
• Synonym万世ばんせいWrittenWhen written 「万世」 and read 「ばんせい」, it appears in 「万世一系」. Solemn in tone; in everyday speech, say 「永遠」.
• Synonym悠久ゆうきゅうWrittenDistant and long-lasting, used of history and nature, as in 「悠久の歴史」. 「永遠」 speaks of an endless future.
• Synonym恒久的こうきゅうてきWrittenLong-lasting and unchanging, typically for institutions and peace, as in 「恒久的な平和」. More written and formal than 「永遠」.
• Synonym無窮むきゅうWrittenEndlessness of time and space, with a solemn ring, as in 「天壌無窮」. More archaic than 「永遠」.
• Synonym永劫えいごうWrittenA Buddhist term for immensely long ages, seen mostly in 「未来永劫」. More archaic than 「永遠」.
• Synonym久遠くおんWrittenInfinitely long time, also the distant past or future, with a religious, literary flavor. More archaic than 「永遠」.
• Synonym万劫ばんごうWrittenA Buddhist term for ages beyond compare, found mainly in religious writing. In everyday speech, say 「永遠」.
• Synonym未来永劫みらいえいごうWrittenA four-character phrase meaning forever from now on. Strong in tone, often used to stress that something will never change.
• Related不変ふへんWrittenFocuses on something never changing in character, as in 「不変の真理」. 「永遠」 stresses the endlessness of time.
• Related限りないかぎりないNeutralAn adjective for boundlessness that mostly modifies feelings or possibilities, as in 「限りない愛」; it is not specifically a word about time.
• Related果てしないはてしないNeutralAn adjective for having no end, used mostly of space or processes, as in 「果てしない道」; 「永遠」 centers on time.
• Related無限むげんNeutralInfinity: no limit in quantity, range, or degree. 「永遠」 is about time without end.
• RelatedとこしえWrittenAn archaic native word for eternity with a waka-like literary air. In daily life, say 「永遠」.
• Related永久とわNeutralObjective and practical rather than lyrical: no end in time, as in 「永久歯」 or 「永久保存」. 「永遠」 carries more emotional weight.
• Related永続的えいぞくてきWrittenLasting a long time, as in 「永続的な関係」, and leaning written. 「永遠」 stresses that something never ends.
• Related果てしがないはてしがないNeutralSynonymous with 「果てしない」 but phrasal in form; mostly says that space or a process has no end.
• Related常しなえとこしなえWrittenAn archaic word for eternity, synonymous with 「常しえ」, with a literary flavor. In daily life, say 「永遠」.
• Related千古不易せんこふえきWrittenA four-character phrase for unchanging through the ages, used of truths and principles. It stresses constancy; 「永遠」 stresses endlessness.
• Related万代ばんだいWrittenFor all generations, with a solemn, congratulatory color, as in 「万代不易」. In everyday speech, say 「永遠」.
• Related生々世々しょうじょうせぜWrittenA rare Buddhist term for life after life, through endless rebirth. 「永遠」 carries no sense of reincarnation.
• RelatedパーマネントNeutralA loanword that in daily use mostly means a perm. For permanence it appears in technical terms; say 「永遠」 or 「永久」 instead.
• Related不易ふえきWrittenWritten language for constancy, seen in 「不易流行」. It stresses being unchanging; 「永遠」 stresses endless time.
• Antonym一瞬いっしゅんNeutralAn instant as brief as a blink, also usable adverbially. The opposite of the endless 「永遠」.
• Antonym刹那せつなWrittenOriginally a Buddhist term for an extremely short instant; more written than 「一瞬」. The opposite of 「永遠」.
• Antonym暫時ざんじWrittenWritten language for a short while; in daily speech say 「しばらく」. The opposite of 「永遠」.

For lyrical eternity use 「永遠」; for objective, practical permanence say 「永久」 (「永久保存」); for lasting institutions and peace, 「恒久」 (「恒久平和」); for what never perishes, 「不滅」; for limitless quantity or degree, 「無限」. 「限りない」 and 「果てしない」 are not specifically about time: they mostly describe feelings, possibilities, space or a process with no end. Archaic literary words like 「久遠」 and 「常しえ」, and set phrases like 「未来永劫」, suit formal or religious prose. The opposites are 「一瞬」 and, in writing, 「刹那」.

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

1. 光ひかりを守まもること。
2. 未来みらいにかけて、ある状態じょうたいがずっと続つづくこと。時間じかんを超越ちょうえつしていること。
3. 時間じかんが限かぎりなく長ながいこと。限かぎりなく長ながい時間じかん。