Questions & Answers about در خانه با آتش بازی نکنید.
How do we make the verb بازی کردن (to play) into the negative command "do not play"?
بازی کردن is a compound verb, so we only change the کردن (to do) part. We take its present stem کن, add the negative command prefix نـ (na-), and add the "you" ending ـید (-id). The word بازی stays right in front, giving us بازی نکنید.
Why is the negative prefix here pronounced "na-" in نکنید (nakonid)?
For negative commands (telling someone not to do something), the prefix is نـ (na-). You might be remembering the regular present tense where "don't" is formed with "ne-" (like نمیکنید or nemikonid). Commands drop the "mi-" and use "na-".
Why does the verb end in ـید (-id) instead of just being نکن (nakon)?
The ـید ending is for the plural "you" (multiple people) or formal singular "you". A safety warning is usually addressed to everyone listening, so the plural form نکنید is used here instead of the singular informal نکن.
What does the word با do in this sentence?
با means "with." Just like in English, you use it to say you are doing an action with an object. Here, با آتش translates directly to "with fire."