What it means
ほかに〜ない states that there is no other person, thing, method, or option besides the one understood from context or specified in the sentence. It commonly appears before a noun followed by は or が and a negative predicate, as in ほかに方法はない, meaning that no other method exists. The expression is useful when emphasizing that the available choice is limited to one possibility.
Usage note
ほかに can also mean “in addition” in affirmative sentences, so the negative predicate is important for the meaning “nothing else.” This pattern should also be distinguished from しか〜ない, which more directly means “only” and requires a negative predicate.
How to use it
この規則のほかに例外を認める根拠はありません。
There is no basis for recognizing an exception other than this rule.
この地域には、ほかに利用できる避難所はありません。
There is no other shelter available for use in this area.
この規則のほかに例外を認める根拠はない。
There is no basis for recognizing an exception other than this rule.
この地域には、ほかに利用できる避難所はない。
There is no other shelter available for use in this area.