開あける describes opening something; 開あく（あく） describes something opening.

The idea

This is an ichidan verb: remove る and add ます or て. Change ます to ません for the polite negative and to ました for the polite past. With 開あける, the object normally takes を: 窓まどを開あけます. With 開あく, the thing that opens takes が: 窓まどが開あきます. 窓まどが開あいています describes the resulting open state. The polite past forms are 開あけました and 開あきました.

Patterns to compare
Dictionary formPolite non-pastPolite negativePolite pastて form
開あける開あけます開あけません開あけました開あけて

Examples

  • 子こどもは窓まどを開あけます。The child opens the window.
  • 昨日きのう、窓まどを開あけました。Yesterday I opened the window.
  • 今日きょうは窓まどを開あけません。I will not open the window today.
  • すみません、ドアを開あけてください。Excuse me, please open the door.
  • 父ちちは箱はこを開あけて、中なかを見みます。My father opens the box and looks inside.
  • この箱はこを開あけてもいいですか。May I open this box?

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Watch out

An intransitive sentence does not rule out a cause: 風かぜで窓まどが開あきました says the wind opened it. 開あく also has the different reading ひらく in other uses; this lesson focuses on あく.

Try it yourself

  1. 窓まどを＿。（開あける→ます）

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    開けます

    開あけます is the polite non-past of 開あける; context tells whether it refers to a habit or the future.

  2. 箱はこを＿ください。（開あける→て）

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    開けて

    開あけて is the て form of 開あける. Before ください it forms a polite request.

  3. ドアが＿。（開あきます／開あけます）

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    開きます

    The door is what opens, marked by が, so use 開あきます.

Use it today

Ask permission to open a window, then describe the window opening. Check the particles and verb forms against the table.