I'm writing a manual, and needed to say something to the effect of "at runtime", as in "Some program debugging can only be performed (or is more efficient or accurate when performed) at runtime." (wiki)

I instinctively started typing "ランタイム時に" before realizing that I am essentially saying "at runtime-time", or "at the time of runtime".

Is "ランタイム時" acceptable Japanese? What good alternatives are there in case I don't want to or should not use it?

1 Answer 1


ランタイム時に may not be that bad, but feels awkward as you guessed.

And Japanese ランタイム as a noun tends to mean "runtime library" (such as JRE, .NET Framework) rather than "run time". For example, "Javaランタイムをダウンロードしてインストールしてください".

The normal way to say "at runtime" in that context would be (プログラム)起動中に, 実行時に, etc.

  • 2
    (プログラム)実行中 also sounds good to me.
    – sazarando
    Commented Jul 21, 2016 at 1:37

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