What stem change applies to the verb perder?

The stem change that applies to the verb "perder" is e → ie in the singular forms of the present tense (except for the nosotros form).

Here's a breakdown:

* Yo pierdo (I lose)

* Tú pierdes (You lose)

* Él/Ella/Usted pierde (He/She/You formal lose)

* Nosotros perdemos (We lose)

* Vosotros perdéis (You all lose - only used in Spain)

* Ellos/Ellas/Ustedes pierden (They/You all formal lose)

Note: The stem change only applies to the singular forms. In the plural forms (nosotros, vosotros/vosotras, ellos/ellas/ustedes), the stem remains "perd-" without the change to "pierd-".