出すの

doing/sending

→ 出す

phrase Uncommon #8,416

doing/sending The の nominalizes 出す, turning it into “doing/sending it.” The exact meaning of 出す depends on context, and the phrase is often followed by particles such as を, は, or も. In casual speech, を may be omitted before expressions like 忘れないで.

JA: この手紙を出すのを忘れないで。

EN: Don't forget to mail this letter.

私が出すの頼んでおいた手紙にさ、切手貼るの忘れないでよ。

Don't forget to put a stamp on the letter I asked you to mail.

手紙出すの忘れてたよ。

I forgot to mail the letter.

ネズミを穴から出すのも時間の問題さ

It’s only a matter of time before we get the mouse out of its hole.

— RRR (2022)

その手紙を出すのを忘れるな。

Don't forget to mail that letter.

彼はとても優しい性質で、大きな声を出すのも聞いたことがない。