Except for the prohibition, “ないでください” can also be used as a form of request. However, you would find that the structure is exactly same with we have learned before which probably makes you confused. Thus, practice is necessary to distinguish the difference. Let’s have a look at the following examples.
A: コーヒーでも飲みませんか。(Would you want some coffee?)
B: いいですね。(Sure.)
(Aが砂糖を入れようとしているのを見て) (B saw that A was going to add sugar in the coffee.)
B: あっ、すみません。砂糖は入れないでください。(Sorry, no sugar please.)
A: わかりました。(No problem.)
A: (At a sushi shop) すみません。わさびは入れないでください。(Excuse me, no wasabi please.)
B: はい、承知しました。(Yes, sir/madam.)
Finally, I will introduce some points need to be careful when giving a response by “ないでください”.
A: ここでタバコを吸ってもいいですか。(Can I smoke here?)
B: すみません。吸わないでください。(Sorry, could you please not smoke here?)
A: 窓を開けてもいいですか。(May I open the window?)
B: 花粉が入ってくるので、開けないでください。(Sorry, could you keep it closed as the pollen will float in.)
It is no problem if you use “ないでください” to stop someone from doing something. However, it sounds like a commanding tone so might not appropriate for those who are superior to you.
See you next time.