自動詞・他動詞
Intransitive–transitive verb pairs (開く／開ける)machine translation
FormationIntransitive verb: 〜が + verb／Transitive verb: 〜を + verb
Japanese has many verb pairs that share a root but play different roles: intransitive verbs (自動詞) describe something happening on its own and take the particle が — ドアが開く (the door opens); transitive verbs (他動詞) describe someone acting on a thing and take the particle を — ドアを開ける (to open the door). Translated into Vietnamese, the two sentences often come out the same, so you have to look at the particle to tell which side is being described.
Common N4 pairs: 開く／開ける, 閉まる／閉める, つく／つける, 消える／消す, 始まる／始める, 止まる／止める, 入る／入れる, 出る／出す, 壊れる／壊す, 落ちる／落とす. There is no transformation rule that covers every pair, so the surest approach is to learn the vocabulary in pairs from the start.
Whether you choose the intransitive or the transitive verb depends on what you want to emphasize: 窓が開きました simply reports the event (maybe the wind did it), while 窓を開けました indicates that someone did it. This concept pair is also the key to two other N4 patterns: 〜ている with an intransitive verb describes an ongoing state (ドアが開いている), while 〜てある goes with a transitive verb and implies someone did it deliberately (ドアが開けてある).
Examples
風で窓が開きました。
The window opened because of the wind.
暑いですから、窓を開けてください。
It's hot, so please open the window.
電気を消しましたが、テレビはまだついています。
I turned off the lights, but the TV is still on.