ひとりでに

ひとりでに
adverb
by itself; automatically; of its own accord
change
1. by itself; on its own; without anyone doing anything
Describes something that happens with no one causing it. Typically used of doors, machines, and physical conditions that change without human intervention — often with a hint of surprise or unease.
戸(と)がひとりでに開(あ)いた。
The door opened by itself.
傷(きず)はひとりでに治(なお)るでしょう。
The wound will probably heal on its own.
誰(だれ)も触(さわ)っていないのに、機械(きかい)がひとりでに動(うご)き出(だ)した。
Even though no one touched it, the machine started up by itself.

Composed of 一人(ひとり) (alone) + で + に, but written in kana. Points at the absence of an agent: nobody did it.

Common collocations

Similar words

  • おのずと: naturally, in due course — stresses a natural process leading to an outcome, not the absence of an agent
  • 自然(しぜん)と: naturally — everyday word for outcomes that come about without effort, including feelings
  • 自動的(じどうてき)に: automatically — about a mechanism designed to do it, so no surprise is implied

Related Words

Related: おのずと (naturally; of itself)
Compare: 自然(しぜん)と (naturally)
Compare: 自動的(じどうてき) (automatically)
Compare: 自然(しぜん)に (naturally)
Compare: おのずから (naturally)
general
Added 2026.8.1 6:20 · Revised 2026.9.2 13:02
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