Stem-changing Spanish o > ue verbs in the present tense
A number of Spanish verbs are semi-regular because they undergo a stem change (o > ue) in the present tense in all forms except nosotros and vosotros, but the usual endings still apply.
NOTE: The verb jugar (to play) follows almost the same pattern (u > ue), but as it is the only u > ue verb we've decided to include it with the o > ue verbs so that it doesn't feel too lonely. ;)
The essential verbs poder (can/to be able to) and soler (to usually/tend to [do]) follow this pattern but there are many more:
A1 Spanish verb list: Stem-changing verbs: present tense (o > ue)