Prescriptive infinitive (dobrar, não rasgar)

When reading a manual, recipe, or any set of formal instructions in Portuguese, you will often see commands given using the plain, uninflected infinitive.

This "instructional" or "prescriptive" infinitive gives the text a neutral, objective tone—perfect for impersonal step-by-step guides.

Fold the paper in half to start the origami.
Dobrar o papel ao meio para começar o origami.
Fold each flap on the diagonal.
Dobrar cada aba na diagonal.

Outlining Steps

Because the infinitive doesn't need to be conjugated, outlining a multi-step process is straightforward. Just state the action verb in its base form.

Crease the paper well to create the crease.
Vincar bem o papel para criar o vinco.
Overlap the points to be symmetrical.
Sobrepor as pontas para ficar simétrico.

Negative Instructions

Telling the reader not to do something is just as simple. Place não (or a negative phrase like não... nunca) directly in front of the infinitive, bypassing the complex conjugations of the negative imperative.

Do not tear the paper; just unfold the flap.
Não rasgar o papel; apenas desdobrar a aba.
Do not ever reverse the bird; just press.
Não inverter nunca o pássaro; apenas pressionar.