but to the state that resulted from the event ("has eaten" or "is/has been eaten"). In Germanic, the aorist eventually disappeared and merged with the present, while the perfect took on a past tense meaning and became a general past tense. The strong Germanic present thus descends from the PIE present, while the past descends from the PIE perfect. The inflections of PIE verbs also changed considerably. In the course of these changes, the different root-vowels caused by PIE ablaut became markers of tense. Thus in Germanic, *bʰer- became in the infinitive (e-grade); *bar in the past singular (o-grade); *bērun in the past plural (ē-grade); and *buranaz in the past participle (zero-grade). In Proto-Germanic, the system of strong verbs was largely regular. As sound changes took place in the development of Germanic from PIE, the vowels of strong verbs became more varied, but usually in predictable ways, so in most cases all of the principal parts of a strong verb of a given class could be reliably predicted from the infinitive. Thus we can reconstruct Common Germanic as having seven coherent classes of strong verbs. This system continued largely intact in the first attested Germanic languages, notably Gothic, Old English, Old High German and Old Norse. Gradual disappearance Germanic strong verbs, mostly deriving directly from PIE, are slowly being supplanted by or transformed into weak verbs. As well as developing the strong verb system, Germanic also went on to develop two other classes of verbs: the weak verbs and a third, much smaller, class known as the preterite-present verbs, which are continued in the English auxiliary verbs, e.g. can/could, shall/should, may/might, must. Weak verbs originally derived from other types of word in PIE and originally occurred only in the present aspect. They did not have a perfect aspect, meaning that they came to lack a past tense in Germanic once the perfect had become the past. Not having a past tense at all, they obviously also had no vowel alternations between present and past. To compensate for this, a new type of past tense was eventually created for these verbs by adding a -d- or -t- suffix to the stem. This is why only strong verbs have vowel alternations: their past tense forms descend from the original PIE perfect aspect, while the past tense forms of weak verbs were created later. The development of weak verbs in Germanic meant that