Negation: not, no and don't

नहीं (naheen) means “not” and also “no”. It goes just before the verb.

In the present habitual (“I don't eat”), the small verb हूँ, हो, है or हैं is usually dropped after नहीं: मैं मांस नहीं खाता (main maans naheen khaataa, I don't eat meat). With the plain verb “to be”, you keep it: वह घर पर नहीं है (vah ghar par naheen hai, he isn't at home).

To tell someone not to do something, use मत (mat) with the command form. It is most natural with तुम and तू: मत जाओ or जाओ मत (mat jaao, jaao mat: don't go). With आप, मत is also common in everyday speech.

न (na) is softer and more formal. You will see it on signs and in polite notices, often with a verb ending in -एँ (-en): कृपया यहाँ धूम्रपान न करें (kripyaa yahaan dhoomrapaan na karen, please do not smoke here).

न (na) also appears in the pattern न … न (na … na, neither … nor), and at the end of a sentence as a friendly “right?”: आप आएँगे न? (aap aayenge na?, you'll come, won't you?).

Words like “never”, “nothing” and “nobody” are built with नहीं: कभी नहीं (kabhee naheen, never), कुछ नहीं (kuchh naheen, nothing), कोई नहीं (koee naheen, nobody). Unlike standard English, Hindi uses them with a negative verb: मैंने कुछ नहीं खाया (mainne kuchh naheen khaayaa, I didn't eat anything).