万世|ばんせいbansei[1]atamadaka (head-high)

1. noun, adverball ages; eternity

• Synonym永遠えいえんNeutralThe everyday word for eternity and the most common of this group; fits 「永遠の愛」. More colloquial than 「万世」, without its nuance of succession through the ages.
• Synonym永久えいきゅうNeutralEveryday word stressing that something continues endlessly from a given point, as in 「永久保存」; more practical than 「万世」.
• Synonym悠久ゆうきゅうWrittenWritten word seen in phrases like 「悠久の歴史」; stresses long, unbroken duration rather than eternity across the generations.
• Synonym長久ちょうきゅうWrittenWritten word for long continuance, as in 「武運長久」; stresses simply lasting a long time rather than spanning all ages.
• Synonym永劫えいごうWrittenWritten word for immensely long ages with a Buddhist tinge; mostly seen in 「未来永劫」. More literary than 「万世」.
• Synonym久遠くおんWrittenWritten, Buddhist-tinged word that can point to the distant past or the distant future; covers a wider range than 「万世」.
• Synonym無窮むきゅうWrittenWritten word for endlessness, applicable to space as well as time; 「万世」 is specifically about eternity in time, lasting through all generations.
• Related千代ちよWrittenWritten word for a thousand years and generations, much used in blessings and celebrations, as in the anthem line 「千代に八千代に」.
• Related恒久こうきゅうWrittenWritten word for a state that stays unchanged over the long term, as in 「恒久平和」; focuses on permanence of condition rather than ages of time.
• Related永代えいたいWrittenClose in sense to 「万世」, stressing generation after generation; common in set phrases such as 「永代供養」.
• Related永世えいせいWrittenWritten synonym of 「万世」; also used for lifetime titles in shogi and go.
• Related生々世々しょうじょうせぜWrittenBuddhist-flavoured adverb meaning forever, life after life through the cycle of rebirth; more literary than 「万世」.
• Related永久とわNeutralEveryday word stressing that something continues endlessly from a given point, as in 「永久保存」; more practical than 「万世」.
• Related常世とこよWrittenMythological word: eternal unchangingness, but also the land beyond the sea or the world of the dead; more specialized than 「万世」.
• Related千古せんこWrittenWritten word that can also mean remote antiquity; it looks from ancient times down to the present, so it is not limited to the future.
• Related万古ばんこWrittenWritten word stressing what has held since remotest antiquity, as in 「万古不易」.
• Related万劫ばんごうWrittenRare Buddhist word for endless stretches of time; same meaning as 「永劫」.
• Related万代ばんだいWrittenWritten synonym of 「万世」, typically in blessings for long endurance.
• Related未来永劫みらいえいごうWrittenWritten adverbial phrase, forever and ever, stressing continuation into the far future; carries more weight than 「万世」.
• RelatedとこしえWrittenSoft, archaic native-Japanese word for eternity, found mainly in poetry; gentler in tone than 「万世」.
• AntonymひとときNeutralEveryday word for a moment or a short while; the exact opposite of 「万世」 and its sense of eternity through the ages.
• Antonym刹那せつなWrittenBuddhist term for an instant, the briefest possible moment of time; stands directly opposed to 「万世」.

For everyday talk about eternity, 「永遠」 and 「永久」 are the natural choices. 「万世」 is for written, solemn language evoking eternity handed down through the ages, as in 「万世一系」. Among the written synonyms, 「永代」「万代」「永世」 are closest in meaning; the others add Buddhist, mythological or poetic colour. The opposites are 「ひと時」 and 「刹那」.

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

1. 永世えいせい。永久えいきゅう。万代ばんだい。