Hi Wangrong, The phrase you have described are phrases which advise or warn the public against doing something. In general, we tell others: 1. Do not (do something [verb]) OR 2. No (something [noun]) Next, "smoke" can be a verb or a noun. In this case, we use the word as a VERB. Therefore, we say: Do not smoke (verb) We do not write "Do not smoking" because the simple present tense (smoke) is used for something that people may do regularly again and again. Next, "smoking" can be EITHER a verb in the continuous tense OR a gerund (a verb that functions as a noun instead). Therefore, we say: No smoking (gerund, meaning a verb which functions as a noun instead. So, as you can see, it really depends on how you craft the sentence. I hope this helps you. Cheers, Lance

Do not smoke is a normal command or piece of advice that uses correct grammar. Do not smoking is not correct grammar and is not said in English. "Smoking" is the progressive and usually "do not" and the progressive are not used in order like this. Example. "Do not drink" is correct, not "do not drinking" Hopefully this helps!!

Normally, we would say "Do not smoke". Just to let you know, I live in Asia, and I've seen many, many signs like this...so....you must understand that many have a challenge with English! Keep learning!!! :) Regards, David