The verbs ser (to be), ir (to go), and ver (to see) are completely irregular in the imperfect tense. Tables 1 and 2 show the complete imperfect tense forms of the verbs ser and ir, not just the endings. Table 3 shows the complete imperfect tense forms for the verb ver.
The Three Imperfect Irregulars
Notice in Table 3 that ver has the regular endings for an – er verb. With a normal verb, you remove the entire infinitve (– er). What makes ver irregular is that all you remove is the – r from the infinitive ver, and put ve– in front of the regular endings. Since all the regular imperfect endings for – er and – ir verbs have written accent marks, the same is true for ver.