The Indo-European verbal system underwent many radical changes in Early Germanic. In the Germanic languages the verbs are divided into two great classes: Strong and Weak.
The strong verbs form their preterite and past participle by means of ablaut. The weak verbs form their preterite by the addition of a syllable containing a dental (Goth. -da/-ta; OE -de/te) and their past participle by means of a dental suffix, too (Goth. -þ/-t; OE -d/-t).
Besides these two great classes of strong and weak verbs, there are a few other minor groups.
The strong verbs were originally subdivided into reduplicated and non-reduplicated verbs (Goth. letan – lailōt). In OE, the reduplication almost entirely disappeared in the prehistoric period of the language. The non-reduplicated verbs are divided into six classes according to six ablaut-series. The originally reduplicated verbs were put together and called class 7.
The OE verb has the following independent forms (All the forms of the verb were synthetic, as analytical forms were only beginning to appear):
1) one voice (active);
2) two numbers (sg., pl);
3) three persons (distinct forms appear only in sg);
4) two tenses (present and preterite);
5) two complete moods (indicative and subjunctive, the latter originally the IE optative; the imperative mood which is only used in the present tense);
6) three non-finite forms:
the infinitive;
the present participle with active meaning;
the past participle (passive).
The forms of the present were used to indicate present and future actions. But already in OE the present forms of ‘bēon’ (be), ‘sculan’ (shall), ‘willan’ (will) with the infinitive came to be used to express the future.
The past tense (preterite) was used in a most general sense to indicate events in the past, including those which are nowadays expressed by the forms of the Past Continuous, Past Perfect, Present Perfect and other analytical forms.
Grammatical categories of the verb: number, person, mood (indicative, subjunctive, imperative), tense.
The existence of these four grammatical categories is confirmed by consistent opposition of form and meaning. In addition to those categories we must mention two debatable categories: aspect and voice.
In OE, there were word combinations, including ‘habban’, ‘bēon’, ‘weorþan’ (have, be, become) + the past or present participle. The combinations with the present participle were used to describe a prolonged state or action; the combinations with the past participle indicated a state resulting from previous completed action (the forerunners of modern continuous and perfect forms).
These combinations did not form regular oppositions with the simple forms of the verb, so some linguists say they cannot be treated as members of grammatical categories. They belonged to the periphery of the verb system and provided a supply of word combinations which was later used for further extension of the system.
The category of voice in OE is another debatable problem. The only trace of the old synthetic passive forms in OE is ‘hātte’ (sg); ‘hātton (pl)’ (is/was called, are/were called). Otherwise the passive voice was expressed by the forms of ‘bēon; ‘wesan’ (to be), occasionally also ‘weorþan’ (to become), and the past participle.
During the OE period these constructions were gradually transformed into the analytical forms of the passive voice.