Negative informal commands are used to tell people what not to do. Usually this is implied and during regular conversations, we do not tell people: “I am going to use a negative command now;” we simply tell people what not to do by adding a “No” before the verb.
However, if you are asked to use a negative informal command during a test, you will know that if use the “tu,” form and it is used when speaking to someone of your same age, a child, or a student.
These commands are used with verbs ending in ar; er-ir and irregular verbs. When using regular verbs ending in “ar," for example, the word hablar (to speak) you have to remember to conjugate the verb in first person:
“Yo hablo.” Look at the word “hablo” and replace the final “o” with “es,” and you have “hables.” To complete your negative informal command, you add a “No.” No hables. This implies you are directing this command to someone using “tu” as it is implied in the sentence: “No hables (tu), however, remember that we do not use the “tu” word.
For verbs ending in “er - ir” you will remember the form of the verb conjugated in first person. For these verbs, you add “as,” at the end of the verb.
The word “comer,” “to eat,” if you conjugate it in the first person, you have: “yo como.” You simply take the “o” out of the verb and add “as” to the end of the verb.
No comas! - Do not eat!
For verbs ending in “ir,” you will follow the same procedure: Salir – To go out.
Yo salgo - Taking the “o” out and adding “as” to the end of the word, we have:
“No salgas!” Do not go out!
Dormir - Yo duermo - No duermas!