So I was considering the grammar points 間に, うちに and 時に today. I came across this question, which talks about 間に vs うちに (which was already in my grammar book).

I'm more curious about the differences between 時に and these constructs. Specifically, today I wanted to make the sentence "I often make mistakes when I write essays". I wrote


What happens if I write



My current best guess is 時 indicates a general point of time, whereas 間 and 内 represent a specific interval, so 時 is more natural here.

Any ideas? My grammar book describes the difference between 間 and うち, but not how it relates to 時.

  • What's the difference between "at/when" and "while"?
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    Jan 25, 2022 at 2:15

1 Answer 1



When I'm writing an essay, I often make mistakes.

  • 時 refers to a point in time, the point in time where you're writing.
  • に is optional

Using 時 means that the action took place right after, right before, or exactly at that time. In this case, it means 'right after' because you cannot make a mistake before you start writing: context will tell you.


While I'm writing an essay, I often make mistakes.

  • 間 refers to a span of time, the duration of writing.
  • に is not optional.

If に is used, it can have two meanings depending on the verb of the main clause. If it's a punctual verb, as in this case 間違いをする, the action took place instantly at some point in the span of time marked by 間.

In summary, in this case, both sentences mean the same thing, but 時 focuses on a point in time, whereas 間 a span of time, hence the translation:

  • When this happens, something often comes true.

Here, 'happens' refers to the point of time where you're writing.

  • While this is happening, something often comes true.

'this is happening' refers to a span of time.


While I'm writing an essay, I often make mistakes.

  • に is a must

This sounds as if making a mistake, while you're writing, is beneficial because of 内に.

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