Stem-changing Spanish o>u verbs in the simple past tenseIn Spanish there are two common verbs that undergo a vowel change in the simple past but only in the 3rd person singular and plural.
These verbs are morir and dormir.
Morir -> murió/murieron
Dormir -> durmió/durmieron
The other forms are not affected by this change and the endings are also the regular endings for -ir regular verbs.