な

The particle/ending な attached to the dictionary form of a verb is a casual, masculine-protective prohibition. It means 'Don’t do X' and is used for direct admonitions or short commands directed at someone. It is common in conversation among friends, family, or peers and can sound strong or blunt, so use with care. It is not used in polite or formal contexts (use ないでください or 〜てはいけません instead). Note that this form is limited to verbs; it does not apply to adjectives or nouns as-is.