末永く・末長く|すえながくsuenagaku[4]nakadaka (mid-high)

1. adverbforever; everlastingly; for many years to come; ever
   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.

• SynonymずっとCasualEveryday colloquial word for something continuing the whole time; it also compares degrees (far more), and lacks the ceremonial tone of a well-wish.
• SynonymいつまでもNeutralMeans forever, with no set end, and is more colloquial than 「末永く」; it can also describe unwanted things going on indefinitely.
• Synonym永々えいえいNeutralMostly suggests something drawn out or long-winded, as in 「長々と話す」, or the body stretched out; written 「永々」 can mean long years, but well-wishes take 「末永く」.
• Synonym幾久しくいくひさしくFormalSame meaning as 「末永く」 but more solemn and old-fashioned; it is often heard in congratulatory speeches at weddings.
• Related長らくながらくNeutralCovers a long span, usually one lasting up to now, as in 「長らくお待たせしました」; it can also refer to the future.
• Related尽未来際じんみらいさいWrittenA Buddhist term meaning on and on to the end of the future; extremely literary and not used in everyday speech.
• Related千代に八千代にちよにやちよにWrittenFrom classical waka and the national anthem, it wishes for generation upon generation; a poetic phrase not used in daily conversation.
• Antonym短くNeutralThe adverbial form of the adjective for 'short': brief in time or length. It states plain fact and carries no sense of well-wishing.
• Antonym一時的にNeutralMeans only temporary or momentary, the direct opposite of 「末永く」's lasting on and on.

Use 「末永く」 to wish that something lasts long; for a more formal, ceremonial touch, as in wedding speeches, use 「幾久しく」. In everyday speech say 「ずっと」 or 「いつまでも」, and use 「長らく」 for a long stretch that has already passed.

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

1. 幾久いくひさしく。遠とおい将来しょうらいまで長ながく。いつまでも。