The present tense subjunctive nosotros/nosotras form is used to give a command addressed to a group that includes the speaker. To create an affirmative command such as this in English, you place “let's” in front of the verb:
To make a negative command of this type in English, you use “let's not”:
Spanish speakers simply use the “we” form of the subjunctive to indicate “let's”:
The negative command is formed in the same way, but with a no or other negative word placed in front.
One exception to the above rule is the verb ir, whose subjunctive form is used only for the negative nosotros/nosotras command. The affirmative nosotros/nosotras command is the indicative form: vamos.
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Vamos a la fiesta esta noche.
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Let's go to the party tonight.
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Tengo prisa. No vayamos al centro comercial primero.
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I'm in a hurry. Let's not go to the mall first.
The affirmative nosotros/nosotras command form of a reflexive verb attaches the reflexive pronoun nos to the end of the subjunctive nosotros/nosotras form of the verb. This creates a tongue twister, so Spanish speakers drop the s that would have preceded the nos.
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Sentémonos en la primera fila.
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Let's sit in the first row.
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Vistámonos como piratas este año.
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Let's dress as pirates this year.
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Casémonos en Jamaica en la playa.
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Let's get married in Jamaica on the beach.
Even though the affirmative nosotros/nosotras command form of ir is irregular, it is still necessary to drop the s in front of the pronoun nos.
However, because the negative command requires the pronoun to precede the subjunctive nosotros/nosotras form, there is no need to drop any letters in this case.
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No nos olvidemos del horno cuando salgamos.
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Let's not forget about the oven when we leave.
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No nos durmamos durante su presentación.
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Let's not fall asleep during his presentation.
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