Verb Pairs 1: 開ける・開く

Many Japanese verbs come in pairs that share a kanji. The transitive verb says that someone acts on an object, and the object takes を: 窓を開けました (I opened the window). The intransitive verb says that something happens or changes by itself, and that thing is the subject with が: ドアが開きました (the door opened).

So look for を in the sentence: with a を object, use the transitive verb; without one, use the intransitive verb, usually with が:

• を → 開ける, 閉める, つける, 消す, 始める, 止める, 入れる, 出す, 落とす, 壊す
• が → 開く, 閉まる, つく, 消える, 始まる, 止まる, 入る, 出る, 落ちる, 壊れる

In a pair, the verb ending in -su is the transitive one, and the verb ending in -aru is the intransitive one. Other pairs have no fixed pattern, so learn each pair together. All sentences in this lesson are in the past: 開けました or 開けた.