決して～ない（けっして～ない）

About

決けっして is an adverb that pairs with a negative statement to form the 決けっして～ない pattern.

決けっして～ない is formal, strong in tone, and has four main usages:

① 禁止きんし - Statements of "prohibition"

② 強つよい意志いし - Statements of "strong will"

③ 強つよい否定ひてい - Statements of "strong negation"

④ ～とは限かぎらない - "Not necessarily X" statements

For usage ①, 決けっして～ない generally translates to "do not do X, by any means/under any circumstances".

E.g. お酒さけを飲のんだ後あとは、決けっして運転うんてんしないでください。 "Please do not, by any means, drive after drinking alcohol."

For usage ②, 決けっして～ない generally translates to "never; by any means; under no circumstances".

E.g. あの店みせで食たべたピザの味あじは、決けっして忘わすれない。 "I will never forget the taste of that restaurant's pizza."

For usage ③, 決けっして～ない generally translates to "certainly (will) not".

E.g. こんな素敵すてきなドレス、他ほかでは決けっして見みつけられませんよ。 "You certainly won't find this nice of a dress at other (stores)."

For usage ④, 決けっして～ない generally translates to "not necessarily X/not decidedly X".

E.g. 持田もちださんは決けっして悪わるい人ひとではない。ただ仕事しごとに厳きびしいだけだ。 "Mr. Mochida isn't necessarily a bad person. He's just strict about work."

Compared to the similar adverbs 絶対ぜったいに and 全まったく, 決けっして is more formal in tone, and must always be paired with a negative.

Summary

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  決けっして～ない is formal, and strong in tone

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  決けっして～ない has four main usages: ① 禁止きんし - Statements of "prohibition", ② 強つよい意志いし - Statements of "strong will", ③ 強つよい否定ひてい - Statements of "strong negation", ④ ～とは限かぎらない - "Not necessarily X" statements

• 

  Compared to the similar adverbs 絶対ぜったいに and 全まったく, 決けっして is more formal in tone, and must always be paired with a negative