How to say "forever" in Japanese

• 末永くすえながくCommon
  adverbCovers 'forever' as 'for many years to come': wishing that something good — happiness, a friendship — lasts long into the future. Typical of well-wishes, as to a newly married couple.
  客人きゃくじんたちはその幸しあわせな夫婦ふうふが末永すえながく裕福ゆうふくな人生じんせいを送おくる事ことを祈いのった。↗

  The guests wished the happy couple a long and prosperous life.
• いつまでもJLPT N3approx.Common
  adverbThe broadest of the three: 'forever' or 'eternally' in ordinary sentences, also 'for good' or 'as long as one likes' — something continuing indefinitely. Usually written in kana alone.
  私はいつまでも彼かれの名なを覚おぼえている。↗

  I still bear his name in mind.
• 八千代やちよCommon
  nounA poetic noun for an immensely long span of time — literally 'eight thousand generations' — not the adverb an ordinary sentence needs; seldom the word you want for 'forever', outside poetry and song.

Use 「いつまでも」 for everyday 'forever' in ordinary sentences, 「末永く」 when wishing that something good lasts for many years to come, and 八千代 only in the poetic sense of an immensely long age.

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

• 末永くすえながくforever
• いつまでもforever
• 八千代やちよvery long period
• フォーエバーforever
• 末始終すえしじゅうforever
• 永々えいえいforever
• 幾久しくいくひさしくforever
• 末代までまつだいまでforever
• 尽未来じんみらいeternally
• 生々世々しょうじょうせぜeternity
• やまないalways