http://www.utexas.edu/cola/centers/lrc/eieol/gotol-1-X.html#Got01_GP04

Strong Verb Conjugation

Verbs in WG, as in the other Germanic languages, fall into two categories: strong and weak. These terms have no relation to the same names applied to nouns and adjectives.

There are two tenses: present and preterite. As with other Indo-European languages exhibiting this type of two-tense system, the distinction between preterite and present is the distinction between past and non-past, since the present forms are used for both present and future. This is similar to Modern English 'I am going on vacation next week', where the present tense has future meaning, equivalent to 'will go'. Likewise, the preterite forms subsume the roles of several different tenses in Modern English, such as the simple past 'did', perfect 'has done', and pluperfect 'had done'. There are three moods: indicative, subjunctive, imperative. The moods are formed with either the preterite or present stems, except for the imperative, which only employs the present stem. Generally the past subjunctive forms denote potential completed actions, whereas the present subjunctive has no such implication of completion. This parallels somewhat Modern English 'might have done' vs. 'might do'. There are also two voices in WG: active and (medio)passive.

Strong Verb Classes

As in English, ablaut, or vowel gradation, characterizes the strong verbs of WG. This system employs vowel alternation within a root to signify change in meaning or function. Take, for example, the English forms: sing-sang-sung-song. Within the base s-ng, an i gives present forms, an a past forms, a u the past participle, and o a derived noun. Other verbs may follow the same ablaut pattern in full or in part, e.g. ring-rang-rung (with no o-grade form). Still other verbs follow an entirely different ablaut pattern, e.g. hold-held-held.

There are seven classes of strong verbs. Six of these are characterized solely by ablaut. The seventh is characterized by reduplication, or by reduplication coupled with ablaut. In order to distinguish, then, the different ablaut classes, specific forms are listed illustrating the gradation sequence. This can be accomplished by listing four principal parts, from which all forms of a given verb may be derived:

• 1st Principal Part, from which are derived all forms of the present;
• 2nd Principal Part, from which are derived the finite forms of the preterite singular;
• 3rd Principal Part, from which are derived all non-singular finite forms of the preterite;
• 4th Principal Part, from which is derived the preterite participle.

The forms chosen as principal parts are, respectively, (1) the infinitive, (2) the first (or third) person singular preterite, (3) the first person plural preterite, (4) the nominative singular masculine preterite participle. The different strong verb classes are listed below with verbs illustrating the vowel gradation.

As can be seen, the singular and plural preterite forms of class VII are derived from the same stem. The seventh class functions somewhat differently from the rest, and this will be treated in more detail in a later.

The Mediopassive Voice

The notion of voice concerns the way in which logical action is manifested in a grammatical statement. By 'logical action' is meant action in the abstract, or the underlying process being referred to. Any action may be referred to in a number of ways, and the morphology of the language dictates whether different expressions of the same action may be rendered concisely or through circumlocution. Within the arena of logical action, one may distinguish agent and patient. The agent is the logical actor, the one doing the logical action; the patient, by contrast, is the one undergoing the logical action, the logical recipient. Within the arena of the grammatical action, one distinguishes the (grammatical) subject and the (direct) object. The grammatical subject denotes the one performing the action expressed by the verb in the statement; the direct object denotes the recipient of that verbal action, when different from the grammatical subject. A statement is active when agent and subject are the same. For example, 'I ate the cookie' is active; the logical action is that of 'eating', and 'I' is the agent of this logical action. 'I' is also the subject of the verb expressed: 'ate'. Here the patient, 'the cookie', is the direct object. On the other hand, a statement is passive when patient and subject are the same. For example, 'The cookie was eaten (by me)'. Here again the logical action is 'eating', and 'I' is the agent, while 'the cookie' is still the patient. But now the patient is the subject of the verb expressed: 'was eaten'. The agent, 'I', need not even be expressed, though it is possible with the phrase 'by me'.

A third voice is distinguished, called the middle voice. The middle voice is somewhere between the active and passive voices, where the distinction between agent and patient is blurred. In many of the ancient Indo-European languages, this voice denotes action which is reflexive (e.g. 'you'll get (yourself) killed'), for the personal benefit of the subject (e.g. 'I had a house built'), or representing an internal process (e.g. 'I wondered at its beauty'). In these languages, the morphology denoting the middle voice is often the same as that denoting the passive. Such uses of the morphological passive in Gothic are not very common, and the term mediopassive, rather than simply passive, is employed based largely on historical and comparative grounds.

Like Gothic, WG has a morphological mediopassive only in the present.

A verb is in the mediopassive voice when the subject of the sentence is acted on by the verb. For example in English, "The mirror was broken by the child," the mirror (the subject) receives the action of the verb, and was broken is in the mediopassive voice. In contrast, the same sentence in the active voice would be, "The child broke the mirror."