Stem Changes

Stem-changing verbs in the present subjunctive mostly follow the same pattern you already know from the present indicative. The stem change carries over, but there's an important extra rule for -ir verbs that changes the nosotros form.

-ar and -er Stem Changers

For -ar and -er verbs, the stem change happens only in stressed syllables. Just as in the indicative, the change disappears in nosotros, because the stress falls on the ending rather than on the stem.

Pensar (e → ie)

Notice how the e → ie change disappears in pensemos. This is sometimes called the "boot" pattern, because if you circle the forms that change, the shape looks like a boot.

Volver (o → ue)

-ir Stem Changers: A Special Rule

Here is where -ir verbs diverge from -ar and -er. In the present subjunctive, -ir stem changers have a secondary change in the nosotros form. Specifically:

• e → ie verbs change to e → i in nosotros
• o → ue verbs change to o → u in nosotros
• e → i verbs keep e → i in all forms, including nosotros

This extra twist is unique to -ir verbs and mirrors the changes you see in the third-person preterite.

Dormir (o → ue / o → u)

Notice durmamos, not dormamos. The o → u change appears only in the nosotros form.

Sentir (e → ie / e → i)

Pedir (e → i, all forms)

For e → i verbs like pedir, the change is uniform across all five forms, including nosotros.

Quick Comparison

The easiest way to see the difference between -ar/-er and -ir stem changers is to line up their nosotros forms side by side:

Next, take a look at spelling changes, which affect verbs whose stems would otherwise produce a different sound when combined with the subjunctive endings.