The present time subjunctive of an irregular verb uses as its base the simple past tense verb stem, but with an Umlaut over the stem vowel, if it is a, o, or u. The subjunctive also uses different endings from the simple past for most forms. Thus even verbs with an i, e, or ie stem vowel in the simple past, which can carry no Umlaut, are nevertheless nearly always recognizable as subjunctive forms.