先ほどメールを書いた際に、久々に「過日」と書こうとして、「あれ?先日と何が違うんだっけ?」と疑問に思ったので調べたことを備忘録的に残します。

日(かじつ)」と「先日は、どちらも「少しある日」表す日本語ですが、使い方ニュアンス微妙違いあります。

まず「日」ですがややあらたまっ書き言葉あり、丁寧敬語表現使われること多いです。「日」とき、その出来事が「先日」よりあるどうかはっきりしないものの、少なくとも“今”から距離ある過去あるという印象ます。

また、「先日」のような「最近のあの日」という臨場感よりも、「過去のある日」という抽象的・形式的な響きが強く、ビジネス文書や式典のあいさつ文などでよく使われます。

一方の「先日」ですが日常会話ビジネスやりとりよく使われる言葉で、日前から1~2週間くらいまで出来事使われる一般です。

たとえば「先日ありがとういました」「先日お伝えした通りです」ように、ややカジュアルやり取りメール冒頭などでもよく見かけます。も「最近ことな」すぐ時期イメージ湧く表現となります

1か月ぐらい前のことで忘れているかな?ということなら「過日」、数週間前でおそらく覚えているだろうことは「先日」といったところでしょうか。

When I was writing an email earlier, I found myself about to use the word “kajitsu” (日, meaning “the other day”) for the first time in a while, and it made me wonder—how is it actually different from “senjitsu” (先日)? So I decided to look into it and jot down a quick note for future reference.

Both “kajitsu” and “senjitsu” refer to “a day not too long ago,” but there are subtle differences in nuance and usage.

Starting with “kajitsu,” it’s a more formal, written expression typically used in polite or respectful language. When someone uses “kajitsu,” it doesn’t necessarily indicate that the event happened before “senjitsu,” but it does suggest a certain distance from the present. Compared to “senjitsu,” which brings to mind a specific, recent day, “kajitsu” has a more abstract and formal tone, and it’s often seen in official documents or ceremonial remarks.

On the other hand, “senjitsu” is a more conversational term frequently used in daily speech or casual business correspondence. It typically refers to something that happened a few days ago, or up to a week or two prior. Phrases like “Thank you for the other day” or “As I mentioned the other day” are common examples. The listener will immediately associate the expression with something relatively recent.

So, if you’re referring to something that happened about a month ago and you’re not sure the other person remembers it, “kajitsu” may be more appropriate. But if the event was just a week or two ago and it’s likely still fresh in their memory, “senjitsu” would be the better choice.

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