In the case of a tú command, different forms are used for affirmative commands and negative commands. There is also a special set of commands for the vosotros/vosotras form of tú.
Regular affirmative tú commands
The form used when an affirmative command is given to someone you would address as tú is the most unusually formed, so it's best to start with these. It may seem strange, but the form of the verb used for an affirmative tú command almost always looks like the present tense él form of the verb. For this reason, it is common to use the pronoun tú after the command so you can tell the difference between “he does something” and “you, do something.” For example:
Baila todos los días
He dances every day.
¡Baila tú todos los días!
Dance every day! (addressed to you singular)
You may notice the inverted exclamation points (¡) that are used before writing a command in Spanish. These will also help indicate that the statement is an imperative, or a command form and, as a result, your voice would indicate this if it were a spoken command.
As long as you remember how to create the present tense él form of the verb, you can create the affirmative tú command form because they are almost always the same. This includes the stem‐changing verbs. If a verb stem changes in the present tense, the command form will have the same stem change.
Don't forget that this form is only used when the command is stated affirmatively. If you tell someone whom you address as tú not to do something, it is a negative command, and there is a different form you must use. But first there are, of course, some verbs that have an irregular form for affirmative tú commands.
Irregular affirmative tú commands
There are very few irregular affirmative tú commands that are not identical to the present tense él form of the verb. Table 1 lists the eight most commonly used verbs with irregular affirmative tú commands as well as the equivalent English command.
Notice that the tú command for ser is the same as the present tense yo form of the verb saber. Sometimes the context of the sentence will make it clear which of the two is intended; however, placing the subject pronoun after the command further clarifies the meaning. Notice in the following examples how using a subject pronoun will clarify these identical twins.
Sé tú un buen niño mientras tu madre va de compras.
Be a good boy while your mother goes shopping. (affirmative tú command, ser)
Yo sé la respuesta.
I know the answer. (present tense yo form, saber)
Negative tú commands
The present tense yo form is the base for creating a negative tú command. Most verbs that stem change in the present tense stem change in the yo form, so this will also occur in the negative tú command. In the present tense, the yo form almost always ends in – o. To create a negative tú command, remember this mantra: form of yo, drop the – o, add the opposite ending. Adding the opposite ending means if a verb has an infinitive that ends in – ar, the present tense tú ending for an – er/– ir verb is used to create the negative tú command. If a verb ends in – er or – ir, the present tense tú ending for – ar verbs is used to create a negative tú command.
So, once you remember the yo form, drop the – o ending and use the endings for negative tú commands listed in Table 2.
Here are a few examples:
Be sure to notice that even though an affirmative tú command is like the él form of the verb, a negative tú command uses tú endings, but they use the tú ending of the opposite kind of verb.
Vosotros commands
A vosotros command is used to order a group of people whom you would address in the tú form. The vosotros command forms are unusual because it is much safer to use the ustedes commands with any group.
To create an affirmative vosotros command, replace the – r at the end of the infinitive with a – d. If a verb is reflexive, and the pronoun os is attached, the – d is dropped. Table 3 shows a few examples.
A negative vosotros command is based on the yo form of the verb. Think of the present tense yo form of the verb you want to make into a negative vosotros command, then drop the – o ending and add the vosotros/vosotras ending normally used for the opposite kind of verb. The endings are shown in Table 4.
Following are a few of the verbs commonly used with negative vosotros commands. The infinitive is listed first followed by an example with the verb conjugated in the negative vosotros command form. Notice that when the subject pronoun vosotros is used, it follows the verb.