Several minor groups of verbs can be referred neither to strong nor to weak verbs.
The most important group of these verbs were the so-called "preterite /'pret(ə)rɪt/-presents" or "past-present" verbs. Originally the Present tense forms of these verbs were Past tense forms (or, more precisely, IE perfect forms, denoting past actions relevant for the present). Later these forms acquired a present meaning but preserved many formal features of the Past tense. Most of these verbs had new Past Tense forms built with the help of the dental suffix. Some of them also acquired the forms of the verbals: Participles and Infinitives; most verbs did not have a full paradigm and were in this sense "defective".
The conjugation of OE preterite-presents is shown in Table 15.
The verbs were inflected in the Present like the Past tense of strong verbs: the forms of the 1st and 3rd p. sg were identical and had no ending – yet, unlike strong verbs, they had the same root-vowel in allthe persons; the pl had a different grade of ablaut similarly with strong verbs (which had two distinct stems for the Past: sg and pl). In the Past the preterite-presents were inflected like weak verbs: the dental suffix plus the endings -e, -est, -e. The new Infinitives sculan, cunnan were derived from the pl form. The interchanges of root-vowels in the sg and pl of the Present tense of preterite-present verbs can be traced to the same gradation series as were used in the strong verbs. Before the shift of meaning and time-reference the would-be preterite-presents were strong verbs. The prototype of can may be referred to Class 3 (with the grades [a~u] in the two Past tense stems); the prototype of sculan – to Class 4, ma an – to Class 5, witan, wāt ‘know’ – to Class 1, etc.
In OE there were twelve preterite-present verbs. Six of them have survived in Mod Ε: OE āʒ ; cunnan, cann; dear(r), sculan,sceal; maʒan, mæʒ; mōt (NE owe, ought; can; dare; shall; may; must). Most of the preterite-presents did not indicate actions, but expressed a kind of attitude to an action denoted by another verb, an Infinitive which followed the preterite-present. In other words, they were used like modal verbs, and eventually developed into modern modal verbs. (In OE some of them could also be used as notional verbs, e.g.:
pe him āht sceoldon 'what they owed him'.)