決して～ない【けっして～ない】

The adverb けっして決して (けっして) is used together with a negative form to express strong denial or emphasis, meaning "never", "by no means", or "absolutely not". It always appears with a negative ending – without one, the sentence is ungrammatical.

Basic usage

けっして決して reinforces the negative, making it stronger and more emphatic than simply using 〜～ない alone.

Compare: わすれない忘れない ("I won't forget") vs. けっして決してわすれない忘れない ("I will never forget"). The addition of けっして決して adds emotional weight and conviction.

With adjectives and nouns

While けっして決して most commonly pairs with negative verbs, it can also be used with negative forms of adjectives and noun sentences.

Important notes

• けっして決して must be paired with a negative ending (〜～ない、〜～ません、〜～ではない, etc.). Using it with an affirmative sentence is incorrect.
• It is more formal and emphatic than ぜったいに絶対に〜～ない, which is also strong but used more casually. けっして決して often carries a sense of resolve or solemn declaration.
• In written or formal contexts, けっして決して frequently appears in promises, vows, and firm statements.