Expressions of permission, prohibition, and request

Pola 〜てもいい・〜ないで・〜てください

〜てもいい(〜te mo ii) is used to express permission or allowance. 「〜てもいいです」 means 'may ~'. In the question form 「〜てもいいですか」 is used to ask the listener for permission, and the usual answers are 「はい、どうぞ」 or 「はい、いいですよ」. The word 「いい」 is the core of this pattern, whereas 「いけない」 expresses prohibition. The form is て形(てけい, te-form) + も + いいです. The particle 「も」 is placed between the て形 and 「いい」, for example 「ここで少し休んでもいいです」 (you may rest here for a little while). When asking a teacher or superior, simply use 「〜てもいいですか」, for example 「先生、この辞書を使ってもいいですか」. To say that something does not need to be done, 〜なくてもいいです (there is no need to ~) is used, whereas obligation is expressed with 〜なければなりません (must ~). Both differ from 〜てもいい. The pattern 〜てもらえませんか (could you ~ for me) asks another person to do something for the speaker, so it is not the same as 〜てもいいですか, which asks permission for oneself. Prohibition is expressed with 〜てはいけません and 〜ないでください, which are discussed below. 〜てください(please ~) is used to politely ask the listener to do something. The form is て形 + ください. Ichidan verbs such as 寝る(ねる, to sleep) become 寝て, so 「早く寝てください」 means 'please go to sleep early'. The verb 入る(はいる, to enter) becomes 入って, so 「部屋に入ってください」 means 'please enter the room'. The verb 開ける(あける, to open) becomes 開けて, and 教える(おしえる, to teach) becomes 教えて. To politely ask for help, the same pattern is also used, for example 「少しつめてください」 (please move over a little). When a doctor or staff member gives advice, 〜てください is also used, for example 「毎晩よく眠ってください」. Do not confuse it with 〜ほしい(wanting to have or want) and 〜もらう(to receive), because neither forms a request to the listener. 〜ていてください (please remain in a state of ~) is used to ask the listener to maintain a state, for example 「そのまま座っていてください」 (please stay seated just like that). 〜ています (be ~ing) expresses an action in progress, for example 「今、音楽を聞いています」 (I am listening to music now). A softer prohibition is expressed with 〜ないでください (please do not ~). The form is ない形(ないけい, nai-form) + で + ください. The verb 話す(はなす, to speak) becomes 話さないで, so 「大きい声で話さないでください」 means 'please do not speak in a loud voice'. This pattern often appears in sentence arrangement questions where the position of words must be exact, for example 「ここでは走らないでください」 (please do not run here). To give a suggestion without commanding, 〜といい(です) (it is good to ~) is used: dictionary form verb + と + いいです, for example 「毎朝牛乳を飲むといいですよ」 (it is good to drink milk every morning).