In an earlier lesson you've learned that you can tell that things are forbidden using the て-form + はいけません.
| You must not smoke here. | ここ で タバコ を 吸って は いけません。koko de tabako o sutte wa ikemasen. |
| In Japan, wearing shoes inside the house is not allowed. | 日本 で、 家 の 中 で 靴 を 履いて は いけません。nihon de, ie no naka de kutsu o haite wa ikemasen. |
This is a strict way to express that something must not be done, while at the same time it is formal.
In informal speech, we can say the same by adding 〜ちゃいけない to the て-form stem of a verb. The て-form stem of a verb is obtained by taking the て-form, and then removing the て from the end.
| You must not smoke here. | ここ で タバコ を 吸っちゃ いけない。koko de tabako o sutcha ikenai. |
| In Japan, wearing shoes inside the house is not allowed. | 日本 で、 家 の 中 で 靴 を 履いちゃ いけない。nihon de, ie no naka de kutsu o haicha ikenai. |
If the て-form of a verb ends in で, then we attach 〜じゃいけない instead of 〜ちゃいけない.
| You must not die. | 死んじゃ いけない。shinja ikenai. |
| You're not allowed to play outside. | 外 で 遊んじゃ いけない。soto de asonja ikenai. |
