SuGoiSuす語彙すGrammar › N1 · 14 Set expressions and idioms
〜ないとも限らない: cannot be ruled out
N1 · 14 Set expressions and idioms
Says something unwanted could happen, even if it seems unlikely.
Plain negative form + とも限らない: 事故が起きないとも限らない. Often used for warnings and caution. Positive form is 〜とも限らない (not necessarily). Spoken and written. Similar to 〜かもしれない, but stresses taking care.
Examples
念のため、傘を持っていこう。雨が降らないとも限らない。
Let's take an umbrella just in case; we cannot rule out rain.
いつ地震が起きないとも限らないので、備えが必要だ。
An earthquake could happen at any time, so preparation is necessary.