な is classified as a 終助詞（しゅうじょし）, or ‘sentence ending particle’ in Japanese. When attached to the base (dictionary) form of a verb, it has the nuance of strongly demanding that someone ‘not’ do something.

• 危険（きけん）！触（さわ）るな!
  Danger! Don't touch!
• 「家（いえ）の中（なか）で走（はし）るな！」とお母（かあ）さんが言（い）った。
  My mother said, “Don't run in the house!”