“〜hitori de ni・〜shizen to”: Naturally, On Its Own [JLPT N1]
By Nihongo to Japan · Updated July 3, 2026
A state that occurs naturally without human intervention.
“〜hitori de ni・〜shizen to”: Naturally, On Its Own
「ひとりでに」 and 「自然と (しぜんと)」 are both adverbs meaning “naturally, on its own, without human intervention” — something happening or developing by itself though no one did it. E.g. 「ドアがひとりでに開いた」 (the door opened on its own (no one touched it)), 「練習を重ねれば、自然と上達する」 (practice a lot and you naturally improve), 「傷が自然と治った」 (the wound healed naturally). ⚠️ Contrast with 「勝手に」: 「ひとりでに/自然と」 = automatic, spontaneous (neutral, no human action); 「勝手に」 = arbitrarily (often negative, of a person acting without permission)! ひとりでに is physical/natural automatic occurrence; 自然と is mostly for the natural occurrence of change, ability, emotion.
🧠 Core nuance: no one moved it, it just became so by itself
The core is happening, changing by itself/naturally without human intervention: ① ひとりでに — automatic, by itself (no one touched/did it, yet it happens, mostly physical phenomena: ドアがひとりでに開く = the door opens on its own, 火がひとりでに消えた = the fire went out by itself); ② 自然と (しぜんと) — naturally, unconsciously (happening naturally with time/process, mostly change, ability, emotion: 自然と上達する = naturally improve, 自然と笑顔になる = naturally break into a smile, 自然と涙が出た = tears come unbidden). ⚠️ Both carry ‘non-human, spontaneous,' 自然と more often for ‘a natural result/change after some process.' ⚠️ Contrast with 「勝手に」: 「ひとりでに/自然と」 = automatic, spontaneous (neutral, no human action); 「勝手に」 = arbitrarily, willfully (of ‘a person doing … without permission,' often negative: 勝手に決めるな = don't decide arbitrarily)! ひとりでに is ‘a thing by itself …,' 勝手に is ‘a person arbitrarily …,' entirely different. ⚠️ Both are adverbs modifying a verb.
📌 How to Connect
| Form | Use | Example |
|---|---|---|
| ひとりでに ＋ verb | automatic, by itself 〜 | ひとりでに開く |
| 自然と ＋ verb | naturally 〜 | 自然と上達する |
| (contrast) 勝手に ＋ verb | arbitrarily 〜 (a person, often negative) | 勝手に決める |
💬 Example Sentences
- 鍵をかけたのに、ドアがひとりでに開いた。(Though I locked it, the door opened on its own.) — ひとりでに (physical)
- 練習を重ねれば、自然と上達するものだ。(Practice a lot and you naturally improve.) — 自然と (ability)
- 軽い傷だったので、自然と治った。(It was a light wound, so it healed naturally.) — natural healing
- 楽しい話を聞いて、自然と笑顔になった。(Hearing a fun story, I naturally broke into a smile.) — emotion
- ろうそくの火がひとりでに消えた。(The candle's flame went out on its own.) — ひとりでに
🔄 Compare: ひとりでに vs 自然と vs 勝手に vs おのずから
| Expression | Nuance | Example |
|---|---|---|
| ひとりでに | “automatic, by itself” (no human action, mostly physical) | ドアがひとりでに開く |
| 自然と | “naturally, unconsciously” (mostly change/emotion) | 自然と上達する |
| 勝手に | “arbitrarily, willfully” (a person without permission, often negative) | 勝手に決める |
| おのずから | “naturally” (written, ≒ 自然と) | おのずから明らかだ |
⚠️ Common Mistakes
- Distinguish from 勝手に: ひとりでに/自然と = automatic, spontaneous (no human action, neutral); 勝手に = a person arbitrarily, willfully (often negative) — entirely different!
- ひとりでに leans physical: ひとりでに mostly for physical phenomena happening by themselves (door opening, fire going out).
- 自然と leans change/emotion: 自然と mostly for natural change, ability, emotion after a process (上達, 笑顔, 涙).
- Both adverbs: ひとりでに, 自然と are both adverbs modifying a verb.
💡 Nuance & When to Use
「ひとりでに・自然と」 are both adverbs meaning “naturally, on its own, without human intervention,” something happening by itself though no one did it (ドアがひとりでに開いた, 自然と上達する, 自然と治った). ひとりでに leans physical phenomena happening by themselves; 自然と leans natural change, ability, emotion after a process. ⚠️ Distinguish from the ‘a person arbitrarily, willfully (often negative)' 「勝手に」 — ひとりでに/自然と are non-human spontaneity. A must at N1.
🎯 JLPT Exam Tips
- High-frequency N1: ひとりでに/自然と (adverbs) = naturally, on its own (without human intervention, spontaneous); ひとりでに leans physical, 自然と leans change/emotion.
- Core distinction: ひとりでに/自然と (automatic, spontaneous, neutral) vs 勝手に (a person arbitrarily, willfully, often negative).
- Extension: おのずから = the written ‘naturally' (≒ 自然と); both adverbs.
🖊️ 練習題（5題）
Q1. 「練習を重ねれば、___上達するものだ。」（自然而然）
(A) 自然と (B) 勝手に (C) わざと (D) むりに
Q2. 「ドアがひとりでに開いた」の意味は?
(A) 門自己(沒人碰)打開了
(B) 有人打開門
(C) 門壞了打不開
(D) 故意打開門
Q3. 「ひとりでに」と「勝手に」の違いは?
(A) ひとりでに＝自動/自發(中性);勝手に＝擅自(常負面)
(B) 兩者完全相同
(C) ひとりでに＝擅自
(D) 勝手に＝中性自發
Q4. 「自然と」の後に来やすいのは?
(A) 自發性的變化（笑顔になる・身につく）
(B) 命令
(C) 純假設
(D) 疑問
Q5. 用法が自然なのは?
(A) 傷が自然と治った。 (B) 自然とを食べる。
(C) ひとりでにだ高い。 (D) ひとりでに開けなさい(命令)。
答案解析
1. (A) 自然と ── 自然而然會進步。
2. (A) ── 門自己打開了。
3. (A) ── ひとりでに 中性自發;勝手に 擅自(負面)。
4. (A) ── 後接自發性變化。
5. (A) ── 「傷が自然と治った」正確。