What it means
やしない attaches to a verb stem and expresses a forceful negative, often translated as “absolutely not,” “certainly will not,” or “never.” It adds emotional emphasis such as defiance, indignation, disbelief, or firm conviction, and is stronger than an ordinary negative form. The construction is often used when rejecting a claim or insisting that an action will not occur.
Usage note
やしない is emphatic and is not normally suitable for neutral statements. Its polite counterpart, やしません, retains the emphatic meaning while adding polite style; it should not be confused with an ordinary polite negative ending, which is less forceful.
How to use it
彼はその秘密を決して漏らしやしません。
He will absolutely not reveal that secret.
彼はその秘密を決して漏らしやしない。
He will absolutely not reveal that secret.
Example sentences
私はこの程度の失敗で、研究をあきらめやしない。
I will never give up my research over a failure of this magnitude.
彼はどれほど批判されても、自分の信念を曲げやしない。
No matter how much he is criticized, he will never compromise his convictions.
あの古い写真を、思い出もないのに捨てやしない。
I will absolutely not throw away that old photograph, even though I have no memories of it.