決して～ない: “By no means”

Introduction

Today's grammar is all about denial. You can deny that you ate those cookies, deny that you were out late, and deny that you had anything to do with the great pizza incident of 2024, but... only if you pay attention to this lesson!

決けっして～ない: I will never forget you, (username goes here)

構成こうせい

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  決けっして(negative verb/い-adjective)

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  決けっして(noun/な-adjective) + じゃない・ではない
  Example:
  → あのクッキーは決けっして食たべていません。
  "I certainly did not eat that cookie.”

決けっして is an adverb that comes from the verb 決けっする ("to decide; to determine") and is most commonly used in the 決けっして～ない pattern. The 決けして～ない pattern sounds very strong and formal. Basically, if you were going to deny something in court, you'd probably want to use 決けっして～ない.