～にせよ/ にしろ

About

Both ～にしろ and ～にせよ can be used either once in a sentence, or they can be doubled up to express "Whether X, or whether Y... ". If only one instance is used, ～にしろ・にせよ functions more like "Even if X...".

～にしろ and ～にせよ can attach directly to verbs and い-adjectives. They can attach to nouns/な-adjectives with or without である.

にせよ is slightly more formal than にしろ.

E.g. 子供こどもがしたことにせよ、許ゆるされることではない。 "Even if it was done by a child, it's not something that can be forgiven."

E.g. 相手あいてが年下とししたにしろ、礼儀れいぎは必要ひつようだ。 "Even if your opponent is younger, you must be curteous."

In certain contexts (usually statements featuring 「いくら(adjective)」), ～にしろ・にせよ can be used like "no matter how X".

E.g. いくら忙いそがしいにしろ、返事へんじくらいは返かえしてください。 "No matter how busy (you are), please at least respond."

Summary

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  If only one instance is used, ～にしろ・にせよ functions as "Even if X..."

• 

  ～にしろ and ～にせよ can attach directly to verbs and い-adjectives

• 

  ～にしろ and ～にせよ can attach to nouns/な-adjectives with or without である

• 

  にせよ is slightly more formal than にしろ