Spanish stem-changing verbs chart showing vowel changes in -ar, -er, and -ir verbs in the present tense.

A diagram illustrating Spanish stem-changing verbs, categorized by -ar, -er, and -ir verbs, showing vowel changes in the present tense and examples like pensar (e → ie), perder (e → ie), and sentir (e → ie), with additional notes on verbs that change only in the "yo" form.