Spanish uses a different verb form for positive direct commands (such as "do it") than it does for negative direct commands ("don't do it") in the familiar second-person form, that is, when speaking to tú or vosotros.

Note the differences with the following regular verbs, all of them in the imperative mood. Pronouns in parentheses are optional and are included here for clarity:

• habla (tú) (speak, "you" singular); no hables (don't speak, "you" singular); hablad (vosotros) (speak, "you" plural); no habléis (vosotros) (don't speak, "you" plural)

• come (tú) (eat, "you" singular); no comas (don't eat, "you" singular); comed (vosotros) (eat, "you" plural); no comáis (vosotros) (don't eat, "you" plural)
• vive (tú) (live, "you" singular); no vivas (don't live, "you" singular); vivid (vosotros) (live, "you" plural); no viváis (vosotros) (don't live, "you" plural)

The same endings are usually used for for most of the irregular verbs as well.
Note that the negative form of familiar second-person commands is the same as the present subjunctive form.

Here are some examples of sentences showing the difference with irregular verbs:

• Ve a casa. (Go home, singular) No vayas a casa. (Don't go home.) Id a casa. (Go home, plural) No vayáis a casa. (Don't go home, plural.)
• Hazlo. (Do it.) No lo hagas. (Don't do it.) Hacedlo. (Do it, plural.) No lo hagáis. (Don't do it, plural.)
• Dime. (Tell me.) No me digas. (Don't tell me.) Decidme. (Tell me, plural.) No me digáis. (Don't tell me, plural.)