Translation guide
How to express forgetting to write something in Japanese, covering both forgetting the action and forgetting to include content.
The speaker intended to write something but failed to do so.
The most natural way to say 'forget to write'. Uses the verb 書く (write) nominalized with の, followed by を忘れる.
レポートを書くのを忘れた。
I forgot to write the report.
メールを書くのを忘れないで。
Don't forget to write the email.
The speaker wrote something but omitted a specific detail or item.
書くのを忘れる emphasizes forgetting the action of writing itself. 書き忘れる often implies forgetting to write a specific item within a document. However, they overlap significantly and are often interchangeable.
日記を書くのを忘れた。
I forgot to write my diary (the whole action).
日記に今日の出来事を書き忘れた。
I forgot to write today's events in my diary.
The form 書く忘れる (without の or こと) is ungrammatical. Always use 書くのを忘れる, 書くことを忘れる, or the compound verb 書き忘れる.
A slightly more formal alternative using こと to nominalize the verb. Interchangeable with 書くのを忘れる in most contexts.
手紙を書くことを忘れていました。
I forgot to write the letter.
A compound verb meaning 'forget to write'. More concise and often used in casual speech.
宿題を書き忘れた。
I forgot to write my homework.
Please don't forget to write your address.
Can also be used for forgetting to include something, but 書き忘れる is more common for this nuance.
その点を書くのを忘れた。
I forgot to write that point.