質問: Like the title says, I'd like to know the difference in nuance and usage between 「することはない」 and 「しなくてもいい」。 For example: 「謝らなくてもいいよ」 vs. 「謝ることはないよ」 To me, they both sound like "You don't have to apologize [for that]." On one hand, 「...なくてもいい」 sounds slightly more conversational, but I think I've heard 「...ことはない」 in conversation too. Also, in this answer, it says that 「...ことはない」 might have the nuance of something you don't have to do and probably shouldn't do. So maybe 「...なくてもいい」 means that you don't have to do it, but it's fine if you do. Can anyone provide some insights into differences between these two grammar points?
回答: There's a nuance, but most people will probably not give it a second thought. ### 謝らなくてもいいよ * *Don't worry about it.* * *No need to say sorry.* There could be a valid reason to apologize, but it's not a big deal. * 娘{むすめ}: ママの大切{たいせつ}なお皿{さら}を割{わ}ってしまったよ!ごめんなさい。 * 母{はは}: 謝{あやま}らなくていいよ。わざとやったわけじゃないから。 ### 謝ることはないよ * *There's literally nothing to be sorry for.* * ママ: 今日{きょう}パパのビールを買{か}ってくるのを忘{わす}れたわ。謝らなくちゃ。 * 娘{むすめ}: 謝{あやま}ること(は)ないよ。いつも買{か}ってきてあげているじゃない?